Pic16f87x1a

PIC16F87XA
Data Sheet
28/40/44-Pin Enhanced Flash
Microcontrollers
 2003 Microchip Technology Inc. DS39582B

Note the following details of the code protection feature on Microchip devices:
• Microchip products meet the specification contained in their particular Microchip Data Sheet.
• Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
• There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip's Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
• Microchip is willing to work with the customer who is concerned about the integrity of their code.
• Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
products. Attempts to break microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.
Information contained in this publication regarding device
applications and the like is intended through suggestion only
and may be superseded by updates. It is your responsibility to
ensure that your application meets with your specifications.
No representation or warranty is given and no liability is
assumed by Microchip Technology Incorporated with respect
to the accuracy or use of such information, or infringement of
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property rights.
Trademarks
The Microchip name and logo, the Microchip logo, Accuron,
dsPIC, KEELOQ, MPLAB, PIC, PICmicro, PICSTART,
PRO MATE and PowerSmart are registered trademarks of
Microchip Technology Incorporated in the U.S.A. and other
countries.
AmpLab, FilterLab, microID, MXDEV, MXLAB, PICMASTER,
SEEVAL and The Embedded Control Solutions Company are
registered trademarks of Microchip Technology Incorporated
in the U.S.A.
Application Maestro, dsPICDEM, dsPICDEM.net, ECAN,
ECONOMONITOR, FanSense, FlexROM, fuzzyLAB,
In-Circuit Serial Programming, ICSP, ICEPIC, microPort,
Migratable Memory, MPASM, MPLIB, MPLINK, MPSIM,
PICkit, PICDEM, PICDEM.net, PowerCal, PowerInfo,
PowerMate, PowerTool, rfLAB, rfPIC, Select Mode,
SmartSensor, SmartShunt, SmartTel and Total Endurance are
trademarks of Microchip Technology Incorporated in the
U.S.A. and other countries.
Serialized Quick Turn Programming (SQTP) is a service mark
of Microchip Technology Incorporated in the U.S.A.
All other trademarks mentioned herein are property of their
respective companies.
© 2003, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
Printed on recycled paper.
Microchip received QS-9000 quality system
certification for its worldwide headquarters,
design and wafer fabrication facilities in
Chandler and Tempe, Arizona in July 1999
and Mountain View, California in March 2002.
The Company’s quality system processes and
procedures are QS-9000 compliant for its
PICmicro® 8-bit MCUs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals,
non-volatile memory and analog products. In
addition, Microchip’s quality system for the
design and manufacture of development
systems is ISO 9001 certified.
DS39582B-page ii  2003 Microchip Technology Inc.

PIC16F87XA
28/40/44-Pin Enhanced Flash Microcontrollers
Devices Included in this Data Sheet:
• PIC16F873A
• PIC16F874A
• PIC16F876A
• PIC16F877A
High-Performance RISC CPU:
• Only 35 single-word instructions to learn
• All single-cycle instructions except for program
branches, which are two-cycle
• Operating speed: DC – 20 MHz clock input
DC – 200 ns instruction cycle
• Up to 8K x 14 words of Flash Program Memory,
Up to 368 x 8 bytes of Data Memory (RAM),
Up to 256 x 8 bytes of EEPROM Data Memory
• Pinout compatible to other 28-pin or 40/44-pin
PIC16CXXX and PIC16FXXX microcontrollers
Peripheral Features:
• Timer0: 8-bit timer/counter with 8-bit prescaler
• Timer1: 16-bit timer/counter with prescaler,
can be incremented during Sleep via external
crystal/clock
• Timer2: 8-bit timer/counter with 8-bit period
register, prescaler and postscaler
• Two Capture, Compare, PWM modules
- Capture is 16-bit, max. resolution is 12.5 ns
- Compare is 16-bit, max. resolution is 200 ns
- PWM max. resolution is 10-bit
• Synchronous Serial Port (SSP) with SPI™
(Master mode) and I2C™ (Master/Slave)
• Universal Synchronous Asynchronous Receiver
Transmitter (USART/SCI) with 9-bit address
detection
• Parallel Slave Port (PSP) – 8 bits wide with
external RD, WR and CS controls (40/44-pin only)
• Brown-out detection circuitry for
Brown-out Reset (BOR)
Analog Features:
• 10-bit, up to 8-channel Analog-to-Digital
Converter (A/D)
• Brown-out Reset (BOR)
• Analog Comparator module with:
- Two analog comparators
- Programmable on-chip voltage reference
(VREF) module
- Programmable input multiplexing from device
inputs and internal voltage reference
- Comparator outputs are externally accessible
Special Microcontroller Features:
• 100,000 erase/write cycle Enhanced Flash
program memory typical
• 1,000,000 erase/write cycle Data EEPROM
memory typical
• Data EEPROM Retention > 40 years
• Self-reprogrammable under software control
• In-Circuit Serial Programming™ (ICSP™)
via two pins
• Single-supply 5V In-Circuit Serial Programming
• Watchdog Timer (WDT) with its own on-chip RC
oscillator for reliable operation
• Programmable code protection
• Power saving Sleep mode
• Selectable oscillator options
• In-Circuit Debug (ICD) via two pins
CMOS Technology:
• Low-power, high-speed Flash/EEPROM
technology
• Fully static design
• Wide operating voltage range (2.0V to 5.5V)
• Commercial and Industrial temperature ranges
• Low-power consumption
Device
Program Memory Data
SRAM
(Bytes)
EEPROM
(Bytes)
I/O
10-bit
A/D (ch)
CCP
(PWM)
MSSP
USART
Timers
8/16-bit
Comparators
Bytes
# Single Word
Instructions
SPI
Master
I2C
PIC16F873A 7.2K 4096 192 128 22 5 2 Yes Yes Yes 2/1 2
 2003 Microchip Technology Inc. DS39582B-page 1

PIC16F87XA
Pin Diagrams
PIC16F873A/876A
28-Pin PDIP, SOIC, SSOP
1
2
3
4
5
6
7
8
9
10
11
28
27
26
25
24
23
22
21
20
19
18
17
12
13
16
14 15
MCLR/VPP
RA0/AN0
RA1/AN1
RA2/AN2/VREF-/CVREF
RA3/AN3/VREF+
RA4/T0CKI/C1OUT
RA5/AN4/SS/C2OUT
VSS
OSC1/CLKI
OSC2/CLKO
RC0/T1OSO/T1CKI
RC1/T1OSI/CCP2
RC2/CCP1
RC3/SCK/SCL
RB7/PGD
RB6/PGC
RB5
RB4
RB3/PGM
RB2
RB1
RB0/INT
VDD
VSS
RC7/RX/DT
RC6/TX/CK
RC5/SDO
RC4/SDI/SDA
7 MCLR/VPP
1
2
3
4
5
6
28-Pin QFN
RA2/AN2/VREF-/CVREF
RA3/AN3/VREF+
RA4/T0CKI/C1OUT
RA5/AN4/SS/C2OUT
VSS
OSC1/CLKI
RB7/PGD
RB6/PGC
RB5
RB4
22
21 RB3/PGM
20
19
18
17
16
15
RB2
RB1
RB0/INT
VDD
VSS
RC7/RX/DT
RA1/AN1
RA0/AN0
27
PIC16F873A
PIC16F876A
23
RC1/T1OSI/CCP2
26
RC5/SDO
RC6/TX/CK
RC2/CCP1
24
25
RC3/SCK/SCL
RC4/SDI/SDA
28
10
11
8
9
12
13
14
RC0/T1OSO/T1CKI
OSC2/CLKO
1
2
345
6
8 7
RC6/TX/CK
RC5/SDO
RC4/SDI/SDA
RD3/PSP3
RD2/PSP2
RD1/PSP1
RD0/PSP0
RC3/SCK/SCL
RC2/CCP1
RC1/T1OSI/CCP2
RC0/T1OSO/T1CKI
44
43
42
41
40
39
9
10
11
PIC16F874A37
38
36
34
33
32
31
30
29
28
27
26
25
24
23
35
PIC16F877A
18
19
20
21
22
16
17
12
13
14
15
RA3/AN3/VREF+
RA2/AN2/VREF-/CVREF
RA1/AN1
MCLR/VPP
RA0/AN0
RB6/PGC
RB3/PGM
RB7/PGD
RB4
RB5
NC
OSC2/CLKO
OSC1/CLKI
VSS
VSS
VDD
VDD
RE2/CS/AN7
RE1/WR/AN6
RE0/RD/AN5
RA5/AN4/SS/C2OUT
RA4/T0CKI/C1OUT
44-Pin QFN
RC7/RX/DT
RD4/PSP4
RD5/PSP5
RD6/PSP6
RD7/PSP7
VSS
VDD
VDD
RB0/INT
RB1
RB2
DS39582B-page 2  2003 Microchip Technology Inc.

PIC16F87XA
Pin Diagrams (Continued)
RB7/PGD
RB6/PGC
RB5
RB4
RB3/PGM
RB2
RB1
RB0/INT
VDD
VSS
RD7/PSP7
RD6/PSP6
RD5/PSP5
RD4/PSP4
RC7/RX/DT
RC6/TX/CK
RC5/SDO
RC4/SDI/SDA
RD3/PSP3
RD2/PSP2
40-Pin PDIP
MCLR/VPP
RA0/AN0
RA1/AN1
RA2/AN2/VREF-/CVREF
RA3/AN3/VREF+
RA4/T0CKI/C1OUT
RA5/AN4/SS/C2OUT
RE0/RD/AN5
RE1/WR/AN6
RE2/CS/AN7
VDD
VSS
OSC1/CLKI
OSC2/CLKO
RC0/T1OSO/T1CKI
RC1/T1OSI/CCP2
RC2/CCP1
RC3/SCK/SCL
RD0/PSP0
RD1/PSP1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
PIC16F874A/877A
RA2/AN2/VREF-/CVREF
RA1/AN1
RA0/AN0
MCLR/VPP
NC
RB7/PGD
RB6/PGC
RB5
RB4
RB3/PGM
RB2
RB1
RB0/INT
VDD
VSS
RD7/PSP7
RD6/PSP6
RD5/PSP5
RD4/PSP4 RA3/AN3/VREF+
8 7
654321
9
10
11
12
13
14
15
16
17
44
41
NC NC
40
43
42
39
38
37
36
35
34
33
32
31
30
29
PIC16F874A
PIC16F877A
27
28
18
19
20
21
22
23
24
25
26
44-Pin PLCC
RA4/T0CKI/C1OUT
RA5/AN4/SS/C2OUT
RE0/RD/AN5
RE1/WR/AN6
RE2/CS/AN7
VDD
VSS
OSC1/CLKI
OSC2/CLKO
RC0/T1OSO/T1CK1
NC
RC5/SDO
RC6/TX/CK
RC4/SDI/SDA
RD1/PSP1
RD2/PSP2
RD3/PSP3
RD0/PSP0
RC3/SCK/SCL
RC1/T1OSI/CCP2
RC2/CCP1
1
2
345
6
8 7
RC6/TX/CK
RC5/SDO
RC4/SDI/SDA
RD3/PSP3
RD2/PSP2
RD1/PSP1
RD0/PSP0
RC3/SCK/SCL
RC2/CCP1
RC1/T1OSI/CCP2
NC NC
44
43
42
41
40
39
9
10
11
PIC16F874A37
38
PIC16F877A
16
17
35
34
33
32
31
30
29
28
27
26
25
24
23
12
13
14
15
36
18
19
20
21
22
RA2/AN2/VREF-/CVREF
RA3/AN3/VREF+
RA0/AN0
RA1/AN1
MCLR/VPP
NC
RB5
RB6/PGC
RB7/PGD
RB4
NC
RC0/T1OSO/T1CKI
OSC2/CLKO
OSC1/CLKI
VSS
VDD
RE2/CS/AN7
RE1/WR/AN6
RE0/RD/AN5
RA5/AN4/SS/C2OUT
RA4/T0CKI/C1OUT
44-Pin TQFP
RC7/RX/DT
RD4/PSP4
RD5/PSP5
RD6/PSP6
RD7/PSP7
VSS
VDD
RB0/INT
RB1
RB2
RB3/PGM
RC7/RX/DT

PIC16F87XA
Table of Contents
1.0 Device Overview......................................................................................................................................................................... 5
2.0 Memory Organization................................................................................................................................................................ 15
3.0 Data EEPROM and Flash Program Memory ............................................................................................................................ 33
4.0 I/O Ports.................................................................................................................................................................................... 41
5.0 Timer0 Module.......................................................................................................................................................................... 53
6.0 Timer1 Module.......................................................................................................................................................................... 57
7.0 Timer2 Module.......................................................................................................................................................................... 61
8.0 Capture/Compare/PWM Modules............................................................................................................................................. 63
9.0 Master Synchronous Serial Port (MSSP) Module..................................................................................................................... 71
10.0 Addressable Universal Synchronous Asynchronous Receiver Transmitter (USART) ............................................................ 111
11.0 Analog-to-Digital Converter (A/D) Module .............................................................................................................................. 127
12.0 Comparator Module ................................................................................................................................................................ 135
13.0 Comparator Voltage Reference Module ................................................................................................................................. 141
14.0 Special Features of the CPU .................................................................................................................................................. 143
15.0 Instruction Set Summary......................................................................................................................................................... 159
16.0 Development Support ............................................................................................................................................................. 167
17.0 Electrical Characteristics......................................................................................................................................................... 173
18.0 DC and AC Characteristics Graphs and Tables ..................................................................................................................... 197
19.0 Packaging Information ............................................................................................................................................................ 209
Appendix A: Revision History ............................................................................................................................................................ 219
Appendix B: Device Differences........................................................................................................................................................ 219
Appendix C: Conversion Considerations........................................................................................................................................... 220
Index ................................................................................................................................................................................................. 221
On-Line Support................................................................................................................................................................................ 229
Systems Information and Upgrade Hot Line ..................................................................................................................................... 229
Reader Response ............................................................................................................................................................................. 230
PIC16F87XA Product Identification System...................................................................................................................................... 231
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PIC16F87XA
1.0 DEVICE OVERVIEW
This document contains device specific information
about the following devices:
• PIC16F873A
• PIC16F874A
• PIC16F876A
• PIC16F877A
PIC16F873A/876A devices are available only in 28-pin
packages, while PIC16F874A/877A devices are avail-able
in 40-pin and 44-pin packages. All devices in the
PIC16F87XA family share common architecture with
the following differences:
• The PIC16F873A and PIC16F874A have one-half
of the total on-chip memory of the PIC16F876A
and PIC16F877A
• The 28-pin devices have three I/O ports, while the
40/44-pin devices have five
• The 28-pin devices have fourteen interrupts, while
the 40/44-pin devices have fifteen
• The 28-pin devices have five A/D input channels,
while the 40/44-pin devices have eight
• The Parallel Slave Port is implemented only on
the 40/44-pin devices
The available features are summarized in Table 1-1.
Block diagrams of the PIC16F873A/876A and
PIC16F874A/877A devices are provided in Figure 1-1
and Figure 1-2, respectively. The pinouts for these
device families are listed in Table 1-2 and Table 1-3.
Additional information may be found in the PICmicro®
Mid-Range Reference Manual (DS33023), which may
be obtained from your local Microchip Sales Represen-tative
or downloaded from the Microchip web site. The
Reference Manual should be considered a complemen-tary
document to this data sheet and is highly recom-mended
reading for a better understanding of the device
architecture and operation of the peripheral modules.
TABLE 1-1: PIC16F87XA DEVICE FEATURES
Key Features PIC16F873A PIC16F874A PIC16F876A PIC16F877A
Operating Frequency DC – 20 MHz DC – 20 MHz DC – 20 MHz DC – 20 MHz
Resets (and Delays) POR, BOR
(PWRT, OST)
POR, BOR
(PWRT, OST)
POR, BOR
(PWRT, OST)
POR, BOR
(PWRT, OST)
Flash Program Memory
(14-bit words)
4K 4K 8K 8K
Data Memory (bytes) 192 192 368 368
EEPROM Data Memory (bytes) 128 128 256 256
Interrupts 14 15 14 15
I/O Ports Ports A, B, C Ports A, B, C, D, E Ports A, B, C Ports A, B, C, D, E
Timers 3 3 3 3
Capture/Compare/PWM modules 2 2 2 2
Serial Communications MSSP, USART MSSP, USART MSSP, USART MSSP, USART
Parallel Communications — PSP — PSP
10-bit Analog-to-Digital Module 5 input channels 8 input channels 5 input channels 8 input channels
Analog Comparators 2 2 2 2
Instruction Set 35 Instructions 35 Instructions 35 Instructions 35 Instructions
Packages 28-pin PDIP
28-pin SOIC
28-pin SSOP
28-pin QFN
40-pin PDIP
44-pin PLCC
44-pin TQFP
44-pin QFN
28-pin PDIP
28-pin SOIC
28-pin SSOP
28-pin QFN
40-pin PDIP
44-pin PLCC
44-pin TQFP
44-pin QFN

PIC16F87XA
FIGURE 1-1: PIC16F873A/876A BLOCK DIAGRAM
Flash
13 Data Bus 8
Program
Memory
Program 14
Bus
Instruction reg
Program Counter
8 Level Stack
(13-bit)
RAM
File
Registers
Direct Addr 7
RAM Addr(1) 9
Addr MUX
Indirect
Addr
8
FSR reg
Status reg
MUX
ALU
W reg
Power-up
Timer
Oscillator
Start-up Timer
Power-on
Reset
Watchdog
Timer
Instruction
Decode &
Control
Timing
Generation
OSC1/CLKI
OSC2/CLKO
Brown-out
Reset
In-Circuit
Debugger
Low-Voltage
Programming
MCLR VDD, VSS
PORTA
PORTB
PORTC
RA0/AN0
RA1/AN1
RA2/AN2/VREF-/CVREF
RA3/AN3/VREF+
RA4/T0CKI/C1OUT
RA5/AN4/SS/C2OUT
RB0/INT
RB1
RB2
RB3/PGM
RB4
RB5
RB6/PGC
RB7/PGD
RC0/T1OSO/T1CKI
RC1/T1OSI/CCP2
RC2/CCP1
RC3/SCK/SCL
RC4/SDI/SDA
RC5/SDO
RC6/TX/CK
RC7/RX/DT
8
8
3
Timer0 Timer1 Timer2 10-bit A/D
Synchronous
CCP1,2 USART
Serial Port
Data EEPROM
Device Program Flash Data Memory Data EEPROM
PIC16F873A 4K words 192 Bytes 128 Bytes
Note 1: Higher order bits are from the Status register.
Comparator
Voltage
Reference

PIC16F87XA
FIGURE 1-2: PIC16F874A/877A BLOCK DIAGRAM
13 Data Bus 8
Flash
Program
Memory
Program 14
Bus
Instruction reg
Program Counter
8 Level Stack
(13-bit)
RAM
File
Registers
Direct Addr 7
RAM Addr(1) 9
Addr MUX
Indirect
Addr
8
FSR reg
Status reg
MUX
ALU
W reg
Power-up
Timer
Oscillator
Start-up Timer
Power-on
Reset
Watchdog
Timer
Instruction
Decode &
Control
Timing
Generation
OSC1/CLKI
OSC2/CLKO
Brown-out
Reset
In-Circuit
Debugger
Low-Voltage
Programming
MCLR VDD, VSS
PORTA
PORTB
PORTC
PORTD
PORTE
RA0/AN0
RA1/AN1
RA2/AN2/VREF-/CVREF
RA3/AN3/VREF+
RA4/T0CKI/C1OUT
RA5/AN4/SS/C2OUT
RB0/INT
RB1
RB2
RB3/PGM
RB4
RB5
RB6/PGC
RB7/PGD
RC0/T1OSO/T1CKI
RC1/T1OSI/CCP2
RC2/CCP1
RC3/SCK/SCL
RC4/SDI/SDA
RC5/SDO
RC6/TX/CK
RC7/RX/DT
RD0/PSP0
RD1/PSP1
RD2/PSP2
RD3/PSP3
RD4/PSP4
RD5/PSP5
RD6/PSP6
RD7/PSP7
RE0/RD/AN5
RE1/WR/AN6
RE2/CS/AN7
8
8
Timer0 Timer1 Timer2 10-bit A/D
Synchronous
Slave Port
Data EEPROM Comparator
CCP1,2 USART
Serial Port
Device Program Flash Data Memory Data EEPROM
Note 1: Higher order bits are from the Status register.
Parallel
3
Voltage
Reference

PIC16F87XA
TABLE 1-2: PIC16F873A/876A PINOUT DESCRIPTION
Pin Name
PDIP, SOIC,
SSOP Pin#
QFN
Pin#
I/O/P
Type
Buffer
Type
Description
OSC1/CLKI
OSC1
CLKI
9 6
I
I
ST/CMOS(3) Oscillator crystal or external clock input.
Oscillator crystal input or external clock source input. ST
buffer when configured in RC mode; otherwise CMOS.
External clock source input. Always associated with pin
function OSC1 (see OSC1/CLKI, OSC2/CLKO pins).
OSC2/CLKO
OSC2
CLKO
10 7
O
O
— Oscillator crystal or clock output.
Oscillator crystal output. Connects to crystal or resonator
in Crystal Oscillator mode.
In RC mode, OSC2 pin outputs CLKO, which has 1/4 the
frequency of OSC1 and denotes the instruction cycle rate.
MCLR/VPP
MCLR
VPP
1 26
I
P
ST Master Clear (input) or programming voltage (output).
Master Clear (Reset) input. This pin is an active low Reset
to the device.
Programming voltage input.
PORTA is a bidirectional I/O port.
RA0/AN0
RA0
AN0
2 27
I/O
I
TTL
Digital I/O.
Analog input 0.
RA1/AN1
RA1
AN1
3 28
I/O
I
TTL
Digital I/O.
Analog input 1.
RA2/AN2/VREF-/
CVREF
RA2
AN2
VREF-CVREF
4 1
I/O
I
I
O
TTL
Digital I/O.
Analog input 2.
A/D reference voltage (Low) input.
Comparator VREF output.
RA3/AN3/VREF+
RA3
AN3
VREF+
5 2
I/O
I
I
TTL
Digital I/O.
Analog input 3.
A/D reference voltage (High) input.
RA4/T0CKI/C1OUT
RA4
T0CKI
C1OUT
6 3
I/O
I
O
ST
Digital I/O – Open-drain when configured as output.
Timer0 external clock input.
Comparator 1 output.
RA5/AN4/SS/C2OUT
RA5
AN4
SS
C2OUT
7 4
I/O
I
I
O
TTL
Digital I/O.
Analog input 4.
SPI slave select input.
Legend: I = input O = output I/O = input/output P = power
— = Not used TTL = TTL input ST = Schmitt Trigger input
Note 1: This buffer is a Schmitt Trigger input when configured as the external interrupt.
2: This buffer is a Schmitt Trigger input when used in Serial Programming mode.
3: This buffer is a Schmitt Trigger input when configured in RC Oscillator mode and a CMOS input otherwise.

PIC16F87XA
TABLE 1-2: PIC16F873A/876A PINOUT DESCRIPTION (CONTINUED)
Description
PORTB is a bidirectional I/O port. PORTB can be software
programmed for internal weak pull-ups on all inputs.
Pin Name
RB0/INT
RB0
INT
PDIP, SOIC,
SSOP Pin#
QFN
Pin#
21 18
I/O/P
Type
I/O
I
Buffer
Type
TTL/ST(1)
Digital I/O.
External interrupt.
RB1 22 19 I/O TTL Digital I/O.
RB3/PGM
RB3
PGM
24 21
I/O
I
TTL
Digital I/O.
Low-voltage (single-supply) ICSP programming enable pin.
RB6/PGC
RB6
PGC
27 24
I/O
I
TTL/ST(2)
Digital I/O.
In-circuit debugger and ICSP programming clock.
RB7/PGD
RB7
PGD
28 25
I/O
I/O
TTL/ST(2)
Digital I/O.
In-circuit debugger and ICSP programming data.
PORTC is a bidirectional I/O port.
RC0/T1OSO/T1CKI
RC0
T1OSO
T1CKI
11 8
I/O
O
I
ST
Digital I/O.
Timer1 oscillator output.
RC1/T1OSI/CCP2
RC1
T1OSI
CCP2
12 9
I/O
I
I/O
ST
Digital I/O.
Timer1 oscillator input.
Capture2 input, Compare2 output, PWM2 output.
RC2/CCP1
RC2
CCP1
13 10
I/O
I/O
ST
Digital I/O.
RC3/SCK/SCL
RC3
SCK
SCL
14 11
I/O
I/O
I/O
ST
Digital I/O.
Synchronous serial clock input/output for SPI mode.
Synchronous serial clock input/output for I2C mode.
RC4/SDI/SDA
RC4
SDI
SDA
15 12
I/O
I
I/O
ST
Digital I/O.
SPI data in.
I2C data I/O.
RC5/SDO
RC5
SDO
16 13
I/O
O
ST
Digital I/O.
SPI data out.
RC6/TX/CK
RC6
TX
CK
17 14
I/O
O
I/O
ST
Digital I/O.
USART asynchronous transmit.
USART1 synchronous clock.
RC7/RX/DT
RC7
RX
DT
18 15
I/O
I
I/O
ST
Digital I/O.
USART asynchronous receive.
USART synchronous data.
VSS 8, 19 5, 6 P — Ground reference for logic and I/O pins.
VDD 20 17 P — Positive supply for logic and I/O pins.

PIC16F87XA
TABLE 1-3: PIC16F874A/877A PINOUT DESCRIPTION
Pin Name
PDIP
Pin#
PLCC
Pin#
TQFP
Pin#
QFN
Pin#
I/O/P
Type
Buffer
Type
Description
OSC1/CLKI
OSC1
CLKI
13 14 30 32
I
I
ST/CMOS(4) Oscillator crystal or external clock input.
Oscillator crystal input or external clock source
input. ST buffer when configured in RC mode;
otherwise CMOS.
External clock source input. Always associated
with pin function OSC1 (see OSC1/CLKI,
OSC2/CLKO pins).
OSC2/CLKO
OSC2
CLKO
14 15 31 33
O
O
— Oscillator crystal or clock output.
Oscillator crystal output.
Connects to crystal or resonator in Crystal
Oscillator mode.
In RC mode, OSC2 pin outputs CLKO, which
has 1/4 the frequency of OSC1 and denotes the
instruction cycle rate.
MCLR/VPP
MCLR
VPP
1 2 18 18
I
P
ST Master Clear (input) or programming voltage (output).
Master Clear (Reset) input. This pin is an active
low Reset to the device.
Programming voltage input.
PORTA is a bidirectional I/O port.
RA0/AN0
RA0
AN0
2 3 19 19
I/O
I
TTL
Digital I/O.
Analog input 0.
RA1/AN1
RA1
AN1
3 4 20 20
I/O
I
TTL
Digital I/O.
Analog input 1.
RA2/AN2/VREF-/CVREF
RA2
AN2
VREF-CVREF
4 5 21 21
I/O
I
I
O
TTL
Digital I/O.
Analog input 2.
A/D reference voltage (Low) input.
Comparator VREF output.
RA3/AN3/VREF+
RA3
AN3
VREF+
5 6 22 22
I/O
I
I
TTL
Digital I/O.
Analog input 3.
A/D reference voltage (High) input.
RA4/T0CKI/C1OUT
RA4
T0CKI
C1OUT
6 7 23 23
I/O
I
O
ST
Digital I/O – Open-drain when configured as
output.
RA5/AN4/SS/C2OUT
RA5
AN4
SS
C2OUT
7 8 24 24
I/O
I
I
O
TTL
Digital I/O.
Analog input 4.
SPI slave select input.

PIC16F87XA
Description
PORTB is a bidirectional I/O port. PORTB can be
software programmed for internal weak pull-up on all
inputs.
Pin Name
RB0/INT
RB0
INT
PDIP
Pin#
PLCC
Pin#
TQFP
Pin#
QFN
Pin#
33 36 8 9
I/O/P
Type
I/O
I
Buffer
Type
TTL/ST(1)
Digital I/O.
External interrupt.
RB1 34 37 9 10 I/O TTL Digital I/O.
RB3/PGM
RB3
PGM
36 39 11 12
I/O
I
TTL
Digital I/O.
Low-voltage ICSP programming enable pin.
RB6/PGC
RB6
PGC
39 43 16 16
I/O
I
TTL/ST(2)
Digital I/O.
In-circuit debugger and ICSP programming clock.
RB7/PGD
RB7
PGD
40 44 17 17
I/O
I/O
TTL/ST(2)
Digital I/O.
In-circuit debugger and ICSP programming data.

PIC16F87XA
Description
PORTC is a bidirectional I/O port.
Pin Name
RC0/T1OSO/T1CKI
RC0
T1OSO
T1CKI
PDIP
Pin#
PLCC
Pin#
TQFP
Pin#
QFN
Pin#
15 16 32 34
I/O/P
Type
I/O
O
I
Buffer
Type
ST
Digital I/O.
Timer1 oscillator output.
RC1/T1OSI/CCP2
RC1
T1OSI
CCP2
16 18 35 35
I/O
I
I/O
ST
Digital I/O.
Timer1 oscillator input.
RC2/CCP1
RC2
CCP1
17 19 36 36
I/O
I/O
ST
Digital I/O.
RC3/SCK/SCL
RC3
SCK
SCL
18 20 37 37
I/O
I/O
I/O
ST
Digital I/O.
Synchronous serial clock input/output for SPI
mode.
Synchronous serial clock input/output for I2C
mode.
RC4/SDI/SDA
RC4
SDI
SDA
23 25 42 42
I/O
I
I/O
ST
Digital I/O.
SPI data in.
I2C data I/O.
RC5/SDO
RC5
SDO
24 26 43 43
I/O
O
ST
Digital I/O.
SPI data out.
RC6/TX/CK
RC6
TX
CK
25 27 44 44
I/O
O
I/O
ST
Digital I/O.
USART asynchronous transmit.
USART1 synchronous clock.
RC7/RX/DT
RC7
RX
DT
26 29 1 1
I/O
I
I/O
ST
Digital I/O.
USART asynchronous receive.
USART synchronous data.

PIC16F87XA
Description
PORTD is a bidirectional I/O port or Parallel Slave
Port when interfacing to a microprocessor bus.
Pin Name
RD0/PSP0
RD0
PSP0
PDIP
Pin#
PLCC
Pin#
TQFP
Pin#
QFN
Pin#
19 21 38 38
I/O/P
Type
I/O
I/O
Buffer
Type
ST/TTL(3)
Digital I/O.
Parallel Slave Port data.
RD1/PSP1
RD1
PSP1
20 22 39 39
I/O
I/O
ST/TTL(3)
Digital I/O.
RD2/PSP2
RD2
PSP2
21 23 40 40
I/O
I/O
ST/TTL(3)
Digital I/O.
RD3/PSP3
RD3
PSP3
22 24 41 41
I/O
I/O
ST/TTL(3)
Digital I/O.
RD4/PSP4
RD4
PSP4
27 30 2 2
I/O
I/O
ST/TTL(3)
Digital I/O.
RD5/PSP5
RD5
PSP5
28 31 3 3
I/O
I/O
ST/TTL(3)
Digital I/O.
RD6/PSP6
RD6
PSP6
29 32 4 4
I/O
I/O
ST/TTL(3)
Digital I/O.
RD7/PSP7
RD7
PSP7
30 33 5 5
I/O
I/O
ST/TTL(3)
Digital I/O.
PORTE is a bidirectional I/O port.
RE0/RD/AN5
RE0
RD
AN5
8 9 25 25
I/O
I
I
ST/TTL(3)
Digital I/O.
Read control for Parallel Slave Port.
Analog input 5.
RE1/WR/AN6
RE1
WR
AN6
9 10 26 26
I/O
I
I
ST/TTL(3)
Digital I/O.
Write control for Parallel Slave Port.
Analog input 6.
RE2/CS/AN7
RE2
CS
AN7
10 11 27 27
I/O
I
I
ST/TTL(3)
Digital I/O.
Chip select control for Parallel Slave Port.
Analog input 7.
VSS 12, 31 13, 34 6, 29 6, 30,
31
P — Ground reference for logic and I/O pins.
VDD 11, 32 12, 35 7, 28 7, 8,
28, 29
P — Positive supply for logic and I/O pins.
NC — 1, 17,
28, 40
12,13,
33, 34
13 — — These pins are not internally connected. These pins
should be left unconnected.

PIC16F87XA
NOTES:

PIC16F87XA
2.0 MEMORY ORGANIZATION
There are three memory blocks in each of the
PIC16F87XA devices. The program memory and data
memory have separate buses so that concurrent
access can occur and is detailed in this section. The
EEPROM data memory block is detailed in Section 3.0
“Data EEPROM and Flash Program Memory”.
Additional information on device memory may be found
in the PICmicro® Mid-Range MCU Family Reference
Manual (DS33023).
FIGURE 2-1: PIC16F876A/877A
PROGRAM MEMORY MAP
AND STACK
2.1 Program Memory Organization
The PIC16F87XA devices have a 13-bit program
counter capable of addressing an 8K word x 14 bit
program memory space. The PIC16F876A/877A
devices have 8K words x 14 bits of Flash program
memory, while PIC16F873A/874A devices have
4K words x 14 bits. Accessing a location above the
physically implemented address will cause a
wraparound.
The Reset vector is at 0000h and the interrupt vector is
at 0004h.
FIGURE 2-2: PIC16F873A/874A
PROGRAM MEMORY MAP
AND STACK
PC<12:0>
13
0000h
0004h
0005h
CALL, RETURN
RETFIE, RETLW
Stack Level 1
Stack Level 2
Stack Level 8
Reset Vector
Interrupt Vector
On-Chip
07FFh
0800h
0FFFh
1000h
17FFh
1800h
1FFFh
Program
Memory
Page 0
Page 1
Page 2
Page 3
PC<12:0>
13
0000h
0004h
0005h
CALL, RETURN
RETFIE, RETLW
Stack Level 1
Stack Level 2
Stack Level 8
Reset Vector
Interrupt Vector
On-Chip
07FFh
0800h
0FFFh
1000h
1FFFh
Program
Memory
Page 0
Page 1

PIC16F87XA
2.2 Data Memory Organization
The data memory is partitioned into multiple banks
which contain the General Purpose Registers and the
Special Function Registers. Bits RP1 (Status<6>) and
RP0 (Status<5>) are the bank select bits.
Each bank extends up to 7Fh (128 bytes). The lower
locations of each bank are reserved for the Special
Function Registers. Above the Special Function Regis-ters
are General Purpose Registers, implemented as
static RAM. All implemented banks contain Special
Function Registers. Some frequently used Special
Function Registers from one bank may be mirrored in
another bank for code reduction and quicker access.
Note: The EEPROM data memory description can
be found in Section 3.0 “Data EEPROM
and Flash Program Memory” of this data
sheet.
2.2.1 GENERAL PURPOSE REGISTER
FILE
The register file can be accessed either directly, or
indirectly, through the File Select Register (FSR).
RP1:RP0 Bank
00 0
01 1
10 2
11 3

PIC16F87XA
FIGURE 2-3: PIC16F876A/877A REGISTER FILE MAP
File
Address
Indirect addr.(*)
TMR0
PCL
STATUS
FSR
PORTA
PORTB
PORTC
PORTD(1)
PORTE(1)
PCLATH
INTCON
PIR1
PIR2 PIE2
TMR1L
TMR1H
T1CON
TMR2
T2CON
SSPBUF
SSPCON
CCPR1L
CCPR1H
CCP1CON
File
Address
Indirect addr.(*) Indirect addr.(*)
OPTION_REG
PCL
STATUS
FSR
TRISA
TRISB
TRISC
TRISD(1)
TRISE(1)
PCLATH
INTCON
PIE1
PCON
SSPCON2
PR2
SSPADD
SSPSTAT
00h
01h
02h
03h
04h
05h
06h
07h
08h
09h
0Ah
0Bh
0Ch
0Dh
0Eh
0Fh
10h
11h
12h
13h
14h
15h
16h
17h
18h
19h
1Ah
1Bh
1Ch
1Dh
1Eh
1Fh
80h
81h
82h
83h
84h
85h
86h
87h
88h
89h
8Ah
8Bh
8Ch
8Dh
8Eh
8Fh
90h
91h
92h
93h
94h
95h
96h
97h
98h
99h
9Ah
9Bh
9Ch
9Dh
9Eh
9Fh
TXSTA
SPBRG
CMCON
CVRCON
ADRESL
ADCON1
20h A0h
General
Purpose
Register
EEDATA
EEADR
EECON1
EECON2
EEDATH
EEADRH
Reserved(2)
Reserved(2)
File
Address
16 Bytes 16 Bytes
80 Bytes 80 Bytes 80 Bytes
EFh
accesses F0h
70h-7Fh
7Fh FFh
RCSTA
TXREG
RCREG
CCPR2L
CCPR2H
CCP2CON
ADRESH
ADCON0
General
Purpose
Register
96 Bytes
Bank 0 Bank 1
TMR0 OPTION_REG
PCL
STATUS
FSR
PORTB TRISB
PCLATH
INTCON
Indirect addr.(*)
General
Purpose
Register
General
Purpose
Register
General
Purpose
Register
General
Purpose
Register
accesses 1F0h
70h - 7Fh
16Fh
accesses 170h
70h-7Fh
Bank 2 Bank 3
Unimplemented data memory locations, read as ‘0’.
* Not a physical register.
Note 1: These registers are not implemented on the PIC16F876A.
2: These registers are reserved; maintain these registers clear.
File
Address
PCL
STATUS
FSR
PCLATH
INTCON
100h
101h
102h
103h
104h
105h
106h
107h
108h
109h
10Ah
10Bh
10Ch
10Dh
10Eh
10Fh
110h
111h
112h
113h
114h
115h
116h
117h
118h
119h
11Ah
11Bh
11Ch
11Dh
11Eh
11Fh
180h
181h
182h
183h
184h
185h
186h
187h
188h
189h
18Ah
18Bh
18Ch
18Dh
18Eh
18Fh
190h
191h
192h
193h
194h
195h
196h
197h
198h
199h
19Ah
19Bh
19Ch
19Dh
19Eh
19Fh
120h 1A0h
1EFh
17Fh 1FFh

PIC16F87XA
FIGURE 2-4: PIC16F873A/874A REGISTER FILE MAP
File
Address
Indirect addr.(*)
TMR0
PCL
STATUS
FSR
PORTA
PORTB
PORTC
PORTD(1)
PORTE(1)
PCLATH
INTCON
PIR1
PIR2 PIE2
TMR1L
TMR1H
T1CON
TMR2
T2CON
SSPBUF
SSPCON
CCPR1L
CCPR1H
CCP1CON
File
Address
Indirect addr.(*) Indirect addr.(*)
OPTION_REG
PCL
STATUS
FSR
TRISA
TRISB
TRISC
TRISD(1)
TRISE(1)
PCLATH
INTCON
PIE1
PCON
SSPCON2
PR2
SSPADD
SSPSTAT
00h
01h
02h
03h
04h
05h
06h
07h
08h
09h
0Ah
0Bh
0Ch
0Dh
0Eh
0Fh
10h
11h
12h
13h
14h
15h
16h
17h
18h
19h
1Ah
1Bh
1Ch
1Dh
1Eh
1Fh
80h
81h
82h
83h
84h
85h
86h
87h
88h
89h
8Ah
8Bh
8Ch
8Dh
8Eh
8Fh
90h
91h
92h
93h
94h
95h
96h
97h
98h
99h
9Ah
9Bh
9Ch
9Dh
9Eh
9Fh
TXSTA
SPBRG
CMCON
CVRCON
ADRESL
ADCON1
20h A0h
General
Purpose
Register
96 Bytes 96 Bytes
7Fh FFh
RCSTA
TXREG
RCREG
CCPR2L
CCPR2H
CCP2CON
ADRESH
ADCON0
General
Purpose
Register
Bank 0 Bank 1
File
Address
File
Address
TMR0 OPTION_REG
PCL
STATUS
FSR
PORTB TRISB
PCLATH
INTCON
Indirect addr.(*)
PCL
STATUS
FSR
PCLATH
INTCON
100h
101h
102h
103h
104h
105h
106h
107h
108h
109h
10Ah
10Bh
180h
181h
182h
183h
184h
185h
186h
187h
188h
189h
18Ah
18Bh
18Ch
18Dh
18Eh
18Fh
190h
120h 1A0h
1EFh
1F0h
EECON1
EECON2
Reserved(2)
Reserved(2)
accesses
A0h - FFh
10Ch
10Dh
10Eh
10Fh
110h
16Fh
170h
17Fh 1FFh
EEDATA
EEADR
EEDATH
EEADRH
accesses
20h-7Fh
Bank 2 Bank 3
Unimplemented data memory locations, read as ‘0’.
* Not a physical register.
Note 1: These registers are not implemented on the PIC16F873A.
2: These registers are reserved; maintain these registers clear.

PIC16F87XA
2.2.2 SPECIAL FUNCTION REGISTERS
The Special Function Registers are registers used by
the CPU and peripheral modules for controlling the
desired operation of the device. These registers are
implemented as static RAM. A list of these registers is
given in Table 2-1.
The Special Function Registers can be classified into
two sets: core (CPU) and peripheral. Those registers
associated with the core functions are described in
detail in this section. Those related to the operation of
the peripheral features are described in detail in the
peripheral features section.
TABLE 2-1: SPECIAL FUNCTION REGISTER SUMMARY
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Value on:
POR, BOR
Details
on page:
Bank 0
00h(3) INDF Addressing this location uses contents of FSR to address data memory (not a physical register) 0000 0000 31, 150
01h TMR0 Timer0 Module Register xxxx xxxx 55, 150
02h(3) PCL Program Counter (PC) Least Significant Byte 0000 0000 30, 150
03h(3) STATUS IRP RP1 RP0 TO PD Z DC C 0001 1xxx 22, 150
04h(3) FSR Indirect Data Memory Address Pointer xxxx xxxx 31, 150
05h PORTA — — PORTA Data Latch when written: PORTA pins when read --0x 0000 43, 150
06h PORTB PORTB Data Latch when written: PORTB pins when read xxxx xxxx 45, 150
07h PORTC PORTC Data Latch when written: PORTC pins when read xxxx xxxx 47, 150
08h(4) PORTD PORTD Data Latch when written: PORTD pins when read xxxx xxxx 48, 150
09h(4) PORTE — — — — — RE2 RE1 RE0 ---- -xxx 49, 150
0Ah(1,3) PCLATH — — — Write Buffer for the upper 5 bits of the Program Counter ---0 0000 30, 150
0Bh(3) INTCON GIE PEIE TMR0IE INTE RBIE TMR0IF INTF RBIF 0000 000x 24, 150
0Ch PIR1 PSPIF(3) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 26, 150
0Dh PIR2 — CMIF — EEIF BCLIF — — CCP2IF -0-0 0--0 28, 150
0Eh TMR1L Holding Register for the Least Significant Byte of the 16-bit TMR1 Register xxxx xxxx 60, 150
0Fh TMR1H Holding Register for the Most Significant Byte of the 16-bit TMR1 Register xxxx xxxx 60, 150
10h T1CON — — T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON --00 0000 57, 150
11h TMR2 Timer2 Module Register 0000 0000 62, 150
12h T2CON — TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000 61, 150
13h SSPBUF Synchronous Serial Port Receive Buffer/Transmit Register xxxx xxxx 79, 150
14h SSPCON WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 82, 82,
150
15h CCPR1L Capture/Compare/PWM Register 1 (LSB) xxxx xxxx 63, 150
16h CCPR1H Capture/Compare/PWM Register 1 (MSB) xxxx xxxx 63, 150
17h CCP1CON — — CCP1X CCP1Y CCP1M3 CCP1M2 CCP1M1 CCP1M0 --00 0000 64, 150
18h RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 0000 000x 112, 150
19h TXREG USART Transmit Data Register 0000 0000 118, 150
1Ah RCREG USART Receive Data Register 0000 0000 118, 150
1Bh CCPR2L Capture/Compare/PWM Register 2 (LSB) xxxx xxxx 63, 150
1Ch CCPR2H Capture/Compare/PWM Register 2 (MSB) xxxx xxxx 63, 150
1Dh CCP2CON — — CCP2X CCP2Y CCP2M3 CCP2M2 CCP2M1 CCP2M0 --00 0000 64, 150
1Eh ADRESH A/D Result Register High Byte xxxx xxxx 133, 150
1Fh ADCON0 ADCS1 ADCS0 CHS2 CHS1 CHS0 GO/DONE — ADON 0000 00-0 127, 150
Legend: x = unknown, u = unchanged, q = value depends on condition, - = unimplemented, read as ‘0’, r = reserved.
Shaded locations are unimplemented, read as ‘0’.
Note 1: The upper byte of the program counter is not directly accessible. PCLATH is a holding register for the PC<12:8>, whose
contents are transferred to the upper byte of the program counter.
2: Bits PSPIE and PSPIF are reserved on PIC16F873A/876A devices; always maintain these bits clear.
3: These registers can be addressed from any bank.
4: PORTD, PORTE, TRISD and TRISE are not implemented on PIC16F873A/876A devices, read as ‘0’.
5: Bit 4 of EEADRH implemented only on the PIC16F876A/877A devices.

PIC16F87XA
TABLE 2-1: SPECIAL FUNCTION REGISTER SUMMARY (CONTINUED)
Value on:
POR, BOR
Details
on page:
Bank 1
81h OPTION_REG RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0 1111 1111 23, 150
85h TRISA — — PORTA Data Direction Register --11 1111 43, 150
86h TRISB PORTB Data Direction Register 1111 1111 45, 150
87h TRISC PORTC Data Direction Register 1111 1111 47, 150
88h(4) TRISD PORTD Data Direction Register 1111 1111 48, 151
89h(4) TRISE IBF OBF IBOV PSPMODE — PORTE Data Direction bits 0000 -111 50, 151
8Ch PIE1 PSPIE(2) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 0000 0000 25, 151
8Dh PIE2 — CMIE — EEIE BCLIE — — CCP2IE -0-0 0--0 27, 151
8Eh PCON — — — — — — POR BOR ---- --qq 29, 151
8Fh — Unimplemented — —
90h — Unimplemented — —
91h SSPCON2 GCEN ACKSTAT ACKDT ACKEN RCEN PEN RSEN SEN 0000 0000 83, 151
92h PR2 Timer2 Period Register 1111 1111 62, 151
93h SSPADD Synchronous Serial Port (I2C mode) Address Register 0000 0000 79, 151
94h SSPSTAT SMP CKE D/A P S R/W UA BF 0000 0000 79, 151
98h TXSTA CSRC TX9 TXEN SYNC — BRGH TRMT TX9D 0000 -010 111, 151
99h SPBRG Baud Rate Generator Register 0000 0000 113, 151
9Ah — Unimplemented — —
9Bh — Unimplemented — —
9Ch CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 0000 0111 135, 151
9Dh CVRCON CVREN CVROE CVRR — CVR3 CVR2 CVR1 CVR0 000- 0000 141, 151
9Eh ADRESL A/D Result Register Low Byte xxxx xxxx 133, 151
9Fh ADCON1 ADFM ADCS2 — — PCFG3 PCFG2 PCFG1 PCFG0 00-- 0000 128, 151

PIC16F87XA
TABLE 2-1: SPECIAL FUNCTION REGISTER SUMMARY (CONTINUED)
Value on:
POR, BOR
Details
on page:
Bank 2
101h TMR0 Timer0 Module Register xxxx xxxx 55, 150
102h(3) PCL Program Counter’s (PC) Least Significant Byte 0000 0000 30, 150
106h PORTB PORTB Data Latch when written: PORTB pins when read xxxx xxxx 45, 150
10Ch EEDATA EEPROM Data Register Low Byte xxxx xxxx 39, 151
10Dh EEADR EEPROM Address Register Low Byte xxxx xxxx 39, 151
10Eh EEDATH — — EEPROM Data Register High Byte --xx xxxx 39, 151
10Fh EEADRH — — — —(5) EEPROM Address Register High Byte ---- xxxx 39, 151
Bank 3
181h OPTION_REG RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0 1111 1111 23, 150
186h TRISB PORTB Data Direction Register 1111 1111 45, 150
18Ch EECON1 EEPGD — — — WRERR WREN WR RD x--- x000 34, 151
18Dh EECON2 EEPROM Control Register 2 (not a physical register) ---- ---- 39, 151
18Eh — Reserved; maintain clear 0000 0000 —
18Fh — Reserved; maintain clear 0000 0000 —

PIC16F87XA
2.2.2.1 Status Register
The Status register contains the arithmetic status of the
ALU, the Reset status and the bank select bits for data
memory.
The Status register can be the destination for any
instruction, as with any other register. If the Status reg-ister
is the destination for an instruction that affects the
Z, DC or C bits, then the write to these three bits is dis-abled.
These bits are set or cleared according to the
device logic. Furthermore, the TO and PD bits are not
writable, therefore, the result of an instruction with the
Status register as destination may be different than
intended.
For example, CLRF STATUS, will clear the upper three
bits and set the Z bit. This leaves the Status register as
000u u1uu (where u = unchanged).
It is recommended, therefore, that only BCF, BSF,
SWAPF and MOVWF instructions are used to alter the
Status register because these instructions do not affect
the Z, C or DC bits from the Status register. For other
instructions not affecting any status bits, see
Section 15.0 “Instruction Set Summary”.
Note: The C and DC bits operate as a borrow
and digit borrow bit, respectively, in sub-traction.
See the SUBLW and SUBWF
instructions for examples.
REGISTER 2-1: STATUS REGISTER (ADDRESS 03h, 83h, 103h, 183h)
R/W-0 R/W-0 R/W-0 R-1 R-1 R/W-x R/W-x R/W-x
IRP RP1 RP0 TO PD Z DC C
bit 7 bit 0
bit 7 IRP: Register Bank Select bit (used for indirect addressing)
1 = Bank 2, 3 (100h-1FFh)
0 = Bank 0, 1 (00h-FFh)
bit 6-5 RP1:RP0: Register Bank Select bits (used for direct addressing)
11 = Bank 3 (180h-1FFh)
10 = Bank 2 (100h-17Fh)
01 = Bank 1 (80h-FFh)
00 = Bank 0 (00h-7Fh)
Each bank is 128 bytes.
bit 4 TO: Time-out bit
1 = After power-up, CLRWDT instruction or SLEEP instruction
0 = A WDT time-out occurred
bit 3 PD: Power-down bit
1 = After power-up or by the CLRWDT instruction
0 = By execution of the SLEEP instruction
bit 2 Z: Zero bit
1 = The result of an arithmetic or logic operation is zero
0 = The result of an arithmetic or logic operation is not zero
bit 1 DC: Digit carry/borrow bit (ADDWF, ADDLW,SUBLW,SUBWF instructions)
(for borrow, the polarity is reversed)
1 = A carry-out from the 4th low order bit of the result occurred
0 = No carry-out from the 4th low order bit of the result
bit 0 C: Carry/borrow bit (ADDWF, ADDLW,SUBLW,SUBWF instructions)
1 = A carry-out from the Most Significant bit of the result occurred
0 = No carry-out from the Most Significant bit of the result occurred
Note: For borrow, the polarity is reversed. A subtraction is executed by adding the two’s
complement of the second operand. For rotate (RRF, RLF) instructions, this bit is
loaded with either the high, or low order bit of the source register.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
- n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC16F87XA
2.2.2.2 OPTION_REG Register
The OPTION_REG Register is a readable and writable
register, which contains various control bits to configure
the TMR0 prescaler/WDT postscaler (single assign-able
register known also as the prescaler), the external
INT interrupt, TMR0 and the weak pull-ups on PORTB.
Note: To achieve a 1:1 prescaler assignment for
the TMR0 register, assign the prescaler to
the Watchdog Timer.
REGISTER 2-2: OPTION_REG REGISTER (ADDRESS 81h, 181h)
R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0
bit 7 bit 0
bit 7 RBPU: PORTB Pull-up Enable bit
1 = PORTB pull-ups are disabled
0 = PORTB pull-ups are enabled by individual port latch values
bit 6 INTEDG: Interrupt Edge Select bit
1 = Interrupt on rising edge of RB0/INT pin
0 = Interrupt on falling edge of RB0/INT pin
bit 5 T0CS: TMR0 Clock Source Select bit
1 = Transition on RA4/T0CKI pin
0 = Internal instruction cycle clock (CLKO)
bit 4 T0SE: TMR0 Source Edge Select bit
1 = Increment on high-to-low transition on RA4/T0CKI pin
0 = Increment on low-to-high transition on RA4/T0CKI pin
bit 3 PSA: Prescaler Assignment bit
1 = Prescaler is assigned to the WDT
0 = Prescaler is assigned to the Timer0 module
bit 2-0 PS2:PS0: Prescaler Rate Select bits
Bit Value TMR0 Rate WDT Rate
000
001
010
011
100
101
110
111
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
1 : 1
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
Legend:
Note: When using Low-Voltage ICSP Programming (LVP) and the pull-ups on PORTB are
enabled, bit 3 in the TRISB register must be cleared to disable the pull-up on RB3
and ensure the proper operation of the device

PIC16F87XA
2.2.2.3 INTCON Register
The INTCON register is a readable and writable regis-ter,
which contains various enable and flag bits for the
TMR0 register overflow, RB port change and external
RB0/INT pin interrupts.
Note: Interrupt flag bits are set when an interrupt
condition occurs regardless of the state of its
corresponding enable bit or the global
enable bit, GIE (INTCON<7>). User software
should ensure the appropriate interrupt flag
bits are clear prior to enabling an interrupt.
REGISTER 2-3: INTCON REGISTER (ADDRESS 0Bh, 8Bh, 10Bh, 18Bh)
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-x
GIE PEIE TMR0IE INTE RBIE TMR0IF INTF RBIF
bit 7 bit 0
bit 7 GIE: Global Interrupt Enable bit
1 = Enables all unmasked interrupts
0 = Disables all interrupts
bit 6 PEIE: Peripheral Interrupt Enable bit
1 = Enables all unmasked peripheral interrupts
0 = Disables all peripheral interrupts
bit 5 TMR0IE: TMR0 Overflow Interrupt Enable bit
1 = Enables the TMR0 interrupt
0 = Disables the TMR0 interrupt
bit 4 INTE: RB0/INT External Interrupt Enable bit
1 = Enables the RB0/INT external interrupt
0 = Disables the RB0/INT external interrupt
bit 3 RBIE: RB Port Change Interrupt Enable bit
1 = Enables the RB port change interrupt
0 = Disables the RB port change interrupt
bit 2 TMR0IF: TMR0 Overflow Interrupt Flag bit
1 = TMR0 register has overflowed (must be cleared in software)
0 = TMR0 register did not overflow
bit 1 INTF: RB0/INT External Interrupt Flag bit
1 = The RB0/INT external interrupt occurred (must be cleared in software)
0 = The RB0/INT external interrupt did not occur
bit 0 RBIF: RB Port Change Interrupt Flag bit
1 = At least one of the RB7:RB4 pins changed state; a mismatch condition will continue to set
the bit. Reading PORTB will end the mismatch condition and allow the bit to be cleared
(must be cleared in software).
0 = None of the RB7:RB4 pins have changed state
Legend:

PIC16F87XA
2.2.2.4 PIE1 Register
The PIE1 register contains the individual enable bits for
the peripheral interrupts.
REGISTER 2-4: PIE1 REGISTER (ADDRESS 8Ch)
Note: Bit PEIE (INTCON<6>) must be set to
enable any peripheral interrupt.
PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE
bit 7 bit 0
bit 7 PSPIE: Parallel Slave Port Read/Write Interrupt Enable bit(1)
1 = Enables the PSP read/write interrupt
0 = Disables the PSP read/write interrupt
Note 1: PSPIE is reserved on PIC16F873A/876A devices; always maintain this bit clear.
bit 6 ADIE: A/D Converter Interrupt Enable bit
1 = Enables the A/D converter interrupt
0 = Disables the A/D converter interrupt
bit 5 RCIE: USART Receive Interrupt Enable bit
1 = Enables the USART receive interrupt
0 = Disables the USART receive interrupt
bit 4 TXIE: USART Transmit Interrupt Enable bit
1 = Enables the USART transmit interrupt
0 = Disables the USART transmit interrupt
bit 3 SSPIE: Synchronous Serial Port Interrupt Enable bit
1 = Enables the SSP interrupt
0 = Disables the SSP interrupt
bit 2 CCP1IE: CCP1 Interrupt Enable bit
1 = Enables the CCP1 interrupt
0 = Disables the CCP1 interrupt
bit 1 TMR2IE: TMR2 to PR2 Match Interrupt Enable bit
1 = Enables the TMR2 to PR2 match interrupt
0 = Disables the TMR2 to PR2 match interrupt
bit 0 TMR1IE: TMR1 Overflow Interrupt Enable bit
1 = Enables the TMR1 overflow interrupt
0 = Disables the TMR1 overflow interrupt
Legend:

PIC16F87XA
2.2.2.5 PIR1 Register
The PIR1 register contains the individual flag bits for
the peripheral interrupts.
REGISTER 2-5: PIR1 REGISTER (ADDRESS 0Ch)
condition occurs regardless of the state of its
corresponding enable bit or the global
enable bit, GIE (INTCON<7>). User software
should ensure the appropriate interrupt bits
are clear prior to enabling an interrupt.
R/W-0 R/W-0 R-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0
PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF
bit 7 bit 0
bit 7 PSPIF: Parallel Slave Port Read/Write Interrupt Flag bit(1)
1 = A read or a write operation has taken place (must be cleared in software)
0 = No read or write has occurred
Note 1: PSPIF is reserved on PIC16F873A/876A devices; always maintain this bit clear.
bit 6 ADIF: A/D Converter Interrupt Flag bit
1 = An A/D conversion completed
0 = The A/D conversion is not complete
bit 5 RCIF: USART Receive Interrupt Flag bit
1 = The USART receive buffer is full
0 = The USART receive buffer is empty
bit 4 TXIF: USART Transmit Interrupt Flag bit
1 = The USART transmit buffer is empty
0 = The USART transmit buffer is full
bit 3 SSPIF: Synchronous Serial Port (SSP) Interrupt Flag bit
1 = The SSP interrupt condition has occurred and must be cleared in software before returning
from the Interrupt Service Routine. The conditions that will set this bit are:
• SPI – A transmission/reception has taken place.
• I2C Slave – A transmission/reception has taken place.
• I2C Master
- A transmission/reception has taken place.
- The initiated Start condition was completed by the SSP module.
- The initiated Stop condition was completed by the SSP module.
- The initiated Restart condition was completed by the SSP module.
- The initiated Acknowledge condition was completed by the SSP module.
- A Start condition occurred while the SSP module was Idle (multi-master system).
- A Stop condition occurred while the SSP module was Idle (multi-master system).
0 = No SSP interrupt condition has occurred
bit 2 CCP1IF: CCP1 Interrupt Flag bit
Capture mode:
1 = A TMR1 register capture occurred (must be cleared in software)
0 = No TMR1 register capture occurred
Compare mode:
1 = A TMR1 register compare match occurred (must be cleared in software)
0 = No TMR1 register compare match occurred
PWM mode:
Unused in this mode.
bit 1 TMR2IF: TMR2 to PR2 Match Interrupt Flag bit
1 = TMR2 to PR2 match occurred (must be cleared in software)
0 = No TMR2 to PR2 match occurred
bit 0 TMR1IF: TMR1 Overflow Interrupt Flag bit
1 = TMR1 register overflowed (must be cleared in software)
0 = TMR1 register did not overflow
Legend:

PIC16F87XA
2.2.2.6 PIE2 Register
The PIE2 register contains the individual enable bits for
the CCP2 peripheral interrupt, the SSP bus collision
interrupt, EEPROM write operation interrupt and the
comparator interrupt.
REGISTER 2-6: PIE2 REGISTER (ADDRESS 8Dh)
Note: Bit PEIE (INTCON<6>) must be set to
enable any peripheral interrupt.
U-0 R/W-0 U-0 R/W-0 R/W-0 U-0 U-0 R/W-0
— CMIE — EEIE BCLIE — — CCP2IE
bit 7 bit 0
bit 7 Unimplemented: Read as ‘0’
bit 6 CMIE: Comparator Interrupt Enable bit
1 = Enables the comparator interrupt
0 = Disable the comparator interrupt
bit 4 EEIE: EEPROM Write Operation Interrupt Enable bit
1 = Enable EEPROM write interrupt
0 = Disable EEPROM write interrupt
bit 3 BCLIE: Bus Collision Interrupt Enable bit
1 = Enable bus collision interrupt
0 = Disable bus collision interrupt
bit 2-1 Unimplemented: Read as ‘0’
bit 0 CCP2IE: CCP2 Interrupt Enable bit
1 = Enables the CCP2 interrupt
0 = Disables the CCP2 interrupt
Legend:

PIC16F87XA
2.2.2.7 PIR2 Register
The PIR2 register contains the flag bits for the CCP2
interrupt, the SSP bus collision interrupt, EEPROM
write operation interrupt and the comparator interrupt.
REGISTER 2-7: PIR2 REGISTER (ADDRESS 0Dh)
condition occurs regardless of the state of
its corresponding enable bit or the global
enable bit, GIE (INTCON<7>). User
software should ensure the appropriate
interrupt flag bits are clear prior to
enabling an interrupt.
U-0 R/W-0 U-0 R/W-0 R/W-0 U-0 U-0 R/W-0
— CMIF — EEIF BCLIF — — CCP2IF
bit 7 bit 0
bit 6 CMIF: Comparator Interrupt Flag bit
1 = The comparator input has changed (must be cleared in software)
0 = The comparator input has not changed
bit 4 EEIF: EEPROM Write Operation Interrupt Flag bit
1 = The write operation completed (must be cleared in software)
0 = The write operation is not complete or has not been started
bit 3 BCLIF: Bus Collision Interrupt Flag bit
1 = A bus collision has occurred in the SSP when configured for I2C Master mode
0 = No bus collision has occurred
bit 0 CCP2IF: CCP2 Interrupt Flag bit
Capture mode:
1 = A TMR1 register capture occurred (must be cleared in software)
0 = No TMR1 register capture occurred
Compare mode:
1 = A TMR1 register compare match occurred (must be cleared in software)
0 = No TMR1 register compare match occurred
PWM mode:
Unused.
Legend:

PIC16F87XA
2.2.2.8 PCON Register
The Power Control (PCON) register contains flag bits
to allow differentiation between a Power-on Reset
(POR), a Brown-out Reset (BOR), a Watchdog Reset
(WDT) and an external MCLR Reset.
REGISTER 2-8: PCON REGISTER (ADDRESS 8Eh)
Note: BOR is unknown on Power-on Reset. It
must be set by the user and checked on
subsequent Resets to see if BOR is clear,
indicating a brown-out has occurred. The
BOR status bit is a “don’t care” and is not
predictable if the brown-out circuit is dis-abled
(by clearing the BODEN bit in the
configuration word).
U-0 U-0 U-0 U-0 U-0 U-0 R/W-0 R/W-1
— — — — — — POR BOR
bit 7 bit 0
bit 1 POR: Power-on Reset Status bit
1 = No Power-on Reset occurred
0 = A Power-on Reset occurred (must be set in software after a Power-on Reset occurs)
bit 0 BOR: Brown-out Reset Status bit
1 = No Brown-out Reset occurred
0 = A Brown-out Reset occurred (must be set in software after a Brown-out Reset occurs)
Legend:

PIC16F87XA
2.3 PCL and PCLATH
The Program Counter (PC) is 13 bits wide. The low
byte comes from the PCL register which is a readable
and writable register. The upper bits (PC<12:8>) are
not readable, but are indirectly writable through the
PCLATH register. On any Reset, the upper bits of the
PC will be cleared. Figure 2-5 shows the two situations
for the loading of the PC. The upper example in the
figure shows how the PC is loaded on a write to PCL
(PCLATH<4:0> → PCH). The lower example in the
figure shows how the PC is loaded during a CALL or
GOTO instruction (PCLATH<4:3> → PCH).
FIGURE 2-5: LOADING OF PC IN
DIFFERENT SITUATIONS
PC
PCH PCL
12 8 7 0
5
PCLATH<4:0>
PCLATH
Instruction with
PCL as
Destination
ALU
GOTO,CALL
Opcode <10:0>
8
PC
PCH PCL
12 11 10 0
8 7
PCLATH<4:3> 11
2
PCLATH
2.3.1 COMPUTED GOTO
A computed GOTO is accomplished by adding an offset
to the program counter (ADDWF PCL). When doing a
table read using a computed GOTO method, care
should be exercised if the table location crosses a PCL
memory boundary (each 256-byte block). Refer to the
application note, AN556, “Implementing a Table Read”
(DS00556).
2.3.2 STACK
The PIC16F87XA family has an 8-level deep x 13-bit
wide hardware stack. The stack space is not part of
either program or data space and the stack pointer is not
readable or writable. The PC is PUSHed onto the stack
when a CALL instruction is executed, or an interrupt
causes a branch. The stack is POP’ed in the event of a
RETURN, RETLW or a RETFIE instruction execution.
PCLATH is not affected by a PUSH or POP operation.
The stack operates as a circular buffer. This means that
after the stack has been PUSHed eight times, the ninth
push overwrites the value that was stored from the first
push. The tenth push overwrites the second push (and
so on).
Note 1: There are no status bits to indicate stack
overflow or stack underflow conditions.
2: There are no instructions/mnemonics
called PUSH or POP. These are actions
that occur from the execution of the CALL,
RETURN, RETLW and RETFIE instructions
or the vectoring to an interrupt address.
2.4 Program Memory Paging
All PIC16F87XA devices are capable of addressing a
continuous 8K word block of program memory. The
CALL and GOTO instructions provide only 11 bits of
address to allow branching within any 2K program
memory page. When doing a CALL or GOTO instruction,
the upper 2 bits of the address are provided by
PCLATH<4:3>. When doing a CALL or GOTO instruc-tion,
the user must ensure that the page select bits are
programmed so that the desired program memory
page is addressed. If a return from a CALL instruction
(or interrupt) is executed, the entire 13-bit PC is popped
off the stack. Therefore, manipulation of the
PCLATH<4:3> bits is not required for the RETURN
instructions (which POPs the address from the stack).
Note: The contents of the PCLATH register are
unchanged after a RETURN or RETFIE
instruction is executed. The user must
rewrite the contents of the PCLATH regis-ter
for any subsequent subroutine calls or
GOTO instructions.
Example 2-1 shows the calling of a subroutine in
page 1 of the program memory. This example assumes
that PCLATH is saved and restored by the Interrupt
Service Routine (if interrupts are used).
EXAMPLE 2-1: CALL OF A SUBROUTINE
IN PAGE 1 FROM PAGE 0
ORG 0x500
BCF PCLATH,4
BSF PCLATH,3 ;Select page 1
;(800h-FFFh)
CALL SUB1_P1 ;Call subroutine in
: ;page 1 (800h-FFFh)
:
ORG 0x900 ;page 1 (800h-FFFh)
SUB1_P1
: ;called subroutine
;page 1 (800h-FFFh)
:
RETURN ;return to
;Call subroutine
;in page 0
;(000h-7FFh)

PIC16F87XA
2.5 Indirect Addressing, INDF and
FSR Registers
The INDF register is not a physical register. Addressing
the INDF register will cause indirect addressing.
Indirect addressing is possible by using the INDF reg-ister.
Any instruction using the INDF register actually
accesses the register pointed to by the File Select Reg-ister,
FSR. Reading the INDF register itself, indirectly
(FSR = 0) will read 00h. Writing to the INDF register
indirectly results in a no operation (although status bits
may be affected). An effective 9-bit address is obtained
by concatenating the 8-bit FSR register and the IRP bit
(Status<7>) as shown in Figure 2-6.
A simple program to clear RAM locations 20h-2Fh
using indirect addressing is shown in Example 2-2.
EXAMPLE 2-2: INDIRECT ADDRESSING
FIGURE 2-6: DIRECT/INDIRECT ADDRESSING
MOVLW 0x20 ;initialize pointer
MOVWF FSR ;to RAM
NEXT CLRF INDF ;clear INDF register
INCF FSR,F ;inc pointer
BTFSS FSR,4 ;all done?
GOTO NEXT ;no clear next
CONTINUE
: ;yes continue
Direct Addressing Indirect Addressing
RP1:RP0 6 From Opcode 0 IRP 7 FSR Register 0
Bank Select Location Select
Data
Memory(1)
00 01 10 11
80h
FFh
00h
7Fh
100h
17Fh
180h
1FFh
Bank 0 Bank 1 Bank 2 Bank 3
Note 1: For register file map detail, see Figure 2-3.
Bank Select Location Select

PIC16F87XA
NOTES:

PIC16F87XA
3.0 DATA EEPROM AND FLASH
PROGRAM MEMORY
The data EEPROM and Flash program memory is read-able
and writable during normal operation (over the full
VDD range). This memory is not directly mapped in the
register file space. Instead, it is indirectly addressed
through the Special Function Registers. There are six
SFRs used to read and write this memory:
• EECON1
• EECON2
• EEDATA
• EEDATH
• EEADR
• EEADRH
When interfacing to the data memory block, EEDATA
holds the 8-bit data for read/write and EEADR holds the
address of the EEPROM location being accessed.
These devices have 128 or 256 bytes of data EEPROM
(depending on the device), with an address range from
00h to FFh. On devices with 128 bytes, addresses from
80h to FFh are unimplemented and will wraparound to
the beginning of data EEPROM memory. When writing
to unimplemented locations, the on-chip charge pump
will be turned off.
When interfacing the program memory block, the
EEDATA and EEDATH registers form a two-byte word
that holds the 14-bit data for read/write and the EEADR
and EEADRH registers form a two-byte word that holds
the 13-bit address of the program memory location
being accessed. These devices have 4 or 8K words of
program Flash, with an address range from 0000h to
0FFFh for the PIC16F873A/874A and 0000h to 1FFFh
for the PIC16F876A/877A. Addresses above the range
of the respective device will wraparound to the
beginning of program memory.
The EEPROM data memory allows single-byte read and
write. The Flash program memory allows single-word
reads and four-word block writes. Program memory
write operations automatically perform an erase-before-write
on blocks of four words. A byte write in data
EEPROM memory automatically erases the location
and writes the new data (erase-before-write).
The write time is controlled by an on-chip timer. The
write/erase voltages are generated by an on-chip
charge pump, rated to operate over the voltage range
of the device for byte or word operations.
When the device is code-protected, the CPU may
continue to read and write the data EEPROM memory.
Depending on the settings of the write-protect bits, the
device may or may not be able to write certain blocks
of the program memory; however, reads of the program
memory are allowed. When code-protected, the device
programmer can no longer access data or program
memory; this does NOT inhibit internal reads or writes.
3.1 EEADR and EEADRH
The EEADRH:EEADR register pair can address up to
a maximum of 256 bytes of data EEPROM or up to a
maximum of 8K words of program EEPROM. When
selecting a data address value, only the LSByte of the
address is written to the EEADR register. When select-ing
a program address value, the MSByte of the
address is written to the EEADRH register and the
LSByte is written to the EEADR register.
If the device contains less memory than the full address
reach of the address register pair, the Most Significant
bits of the registers are not implemented. For example,
if the device has 128 bytes of data EEPROM, the Most
Significant bit of EEADR is not implemented on access
to data EEPROM.
3.2 EECON1 and EECON2 Registers
EECON1 is the control register for memory accesses.
Control bit, EEPGD, determines if the access will be a
program or data memory access. When clear, as it is
when reset, any subsequent operations will operate on
the data memory. When set, any subsequent
operations will operate on the program memory.
Control bits, RD and WR, initiate read and write or
erase, respectively. These bits cannot be cleared, only
set, in software. They are cleared in hardware at com-pletion
of the read or write operation. The inability to
clear the WR bit in software prevents the accidental,
premature termination of a write operation.
The WREN bit, when set, will allow a write or erase
operation. On power-up, the WREN bit is clear. The
WRERR bit is set when a write (or erase) operation is
interrupted by a MCLR or a WDT Time-out Reset dur-ing
normal operation. In these situations, following
Reset, the user can check the WRERR bit and rewrite
the location. The data and address will be unchanged
in the EEDATA and EEADR registers.
Interrupt flag bit, EEIF in the PIR2 register, is set when
the write is complete. It must be cleared in software.
EECON2 is not a physical register. Reading EECON2
will read all ‘0’s. The EECON2 register is used
exclusively in the EEPROM write sequence.
Note: The self-programming mechanism for Flash
program memory has been changed. On
previous PIC16F87X devices, Flash pro-gramming
was done in single-word erase/
write cycles. The newer PIC18F87XA
devices use a four-word erase/write
cycle. See Section 3.6 “Writing to Flash
Program Memory” for more information.

PIC16F87XA
REGISTER 3-1: EECON1 REGISTER (ADDRESS 18Ch)
R/W-x U-0 U-0 U-0 R/W-x R/W-0 R/S-0 R/S-0
EEPGD — — — WRERR WREN WR RD
bit 7 bit 0
bit 7 EEPGD: Program/Data EEPROM Select bit
1 = Accesses program memory
0 = Accesses data memory
Reads ‘0’ after a POR; this bit cannot be changed while a write operation is in progress.
bit 3 WRERR: EEPROM Error Flag bit
1 = A write operation is prematurely terminated (any MCLR or any WDT Reset during normal
operation)
0 = The write operation completed
bit 2 WREN: EEPROM Write Enable bit
1 = Allows write cycles
0 = Inhibits write to the EEPROM
bit 1 WR: Write Control bit
1 = Initiates a write cycle. The bit is cleared by hardware once write is complete. The WR bit
can only be set (not cleared) in software.
0 = Write cycle to the EEPROM is complete
bit 0 RD: Read Control bit
1 = Initiates an EEPROM read; RD is cleared in hardware. The RD bit can only be set (not
cleared) in software.
0 = Does not initiate an EEPROM read
Legend:

PIC16F87XA
3.3 Reading Data EEPROM Memory
To read a data memory location, the user must write the
address to the EEADR register, clear the EEPGD con-trol
bit (EECON1<7>) and then set control bit RD
(EECON1<0>). The data is available in the very next
cycle in the EEDATA register; therefore, it can be read
in the next instruction (see Example 3-1). EEDATA will
hold this value until another read or until it is written to
by the user (during a write operation).
The steps to reading the EEPROM data memory are:
1. Write the address to EEADR. Make sure that the
address is not larger than the memory size of
the device.
2. Clear the EEPGD bit to point to EEPROM data
memory.
3. Set the RD bit to start the read operation.
4. Read the data from the EEDATA register.
EXAMPLE 3-1: DATA EEPROM READ
BSF STATUS,RP1 ;
BCF STATUS,RP0 ; Bank 2
MOVF DATA_EE_ADDR,W ; Data Memory
MOVWF EEADR ; Address to read
BSF STATUS,RP0 ; Bank 3
BCF EECON1,EEPGD ; Point to Data
; memory
BSF EECON1,RD ; EE Read
MOVF EEDATA,W ; W = EEDATA
3.4 Writing to Data EEPROM Memory
To write an EEPROM data location, the user must first
write the address to the EEADR register and the data to
the EEDATA register. Then the user must follow a
specific write sequence to initiate the write for each byte.
The write will not initiate if the write sequence is not
exactly followed (write 55h to EECON2, write AAh to
EECON2, then set WR bit) for each byte. We strongly
recommend that interrupts be disabled during this
code segment (see Example 3-2).
Additionally, the WREN bit in EECON1 must be set to
enable write. This mechanism prevents accidental
writes to data EEPROM due to errant (unexpected)
code execution (i.e., lost programs). The user should
keep the WREN bit clear at all times, except when
updating EEPROM. The WREN bit is not cleared
by hardware
After a write sequence has been initiated, clearing the
WREN bit will not affect this write cycle. The WR bit will
be inhibited from being set unless the WREN bit is set.
At the completion of the write cycle, the WR bit is
cleared in hardware and the EE Write Complete
Interrupt Flag bit (EEIF) is set. The user can either
enable this interrupt or poll this bit. EEIF must be
cleared by software.
The steps to write to EEPROM data memory are:
1. If step 10 is not implemented, check the WR bit
to see if a write is in progress.
2. Write the address to EEADR. Make sure that the
address is not larger than the memory size of
the device.
3. Write the 8-bit data value to be programmed in
the EEDATA register.
4. Clear the EEPGD bit to point to EEPROM data
memory.
5. Set the WREN bit to enable program operations.
6. Disable interrupts (if enabled).
7. Execute the special five instruction sequence:
• Write 55h to EECON2 in two steps (first
to W, then to EECON2)
• Write AAh to EECON2 in two steps (first
to W, then to EECON2)
• Set the WR bit
8. Enable interrupts (if using interrupts).
9. Clear the WREN bit to disable program
operations.
10. At the completion of the write cycle, the WR bit
is cleared and the EEIF interrupt flag bit is set.
(EEIF must be cleared by firmware.) If step 1 is
not implemented, then firmware should check
for EEIF to be set, or WR to clear, to indicate the
end of the program cycle.
EXAMPLE 3-2: DATA EEPROM WRITE
BSF STATUS,RP1 ;
BSF STATUS,RP0
BTFSC EECON1,WR ;Wait for write
GOTO $-1 ;to complete
BCF STATUS, RP0 ;Bank 2
MOVF DATA_EE_ADDR,W ;Data Memory
MOVWF EEADR ;Address to write
MOVF DATA_EE_DATA,W ;Data Memory Value
MOVWF EEDATA ;to write
BSF STATUS,RP0 ;Bank 3
BCF EECON1,EEPGD ;Point to DATA
;memory
BSF EECON1,WREN ;Enable writes
BCF INTCON,GIE ;Disable INTs.
MOVLW 55h ;
MOVWF EECON2 ;Write 55h
MOVLW AAh ;
MOVWF EECON2 ;Write AAh
BSF EECON1,WR ;Set WR bit to
;begin write
BSF INTCON,GIE ;Enable INTs.
BCF EECON1,WREN ;Disable writes
Required
Sequence

PIC16F87XA
3.5 Reading Flash Program Memory
To read a program memory location, the user must write
two bytes of the address to the EEADR and EEADRH
registers, set the EEPGD control bit (EECON1<7>) and
then set control bit RD (EECON1<0>). Once the read
control bit is set, the program memory Flash controller
will use the next two instruction cycles to read the data.
This causes these two instructions immediately follow-ing
the “BSF EECON1,RD” instruction to be ignored.
The data is available in the very next cycle in the
EEDATA and EEDATH registers; therefore, it can be
read as two bytes in the following instructions. EEDATA
and EEDATH registers will hold this value until another
read or until it is written to by the user (during a write
operation).
EXAMPLE 3-3: FLASH PROGRAM READ
BSF STATUS, RP1 ;
BCF STATUS, RP0 ; Bank 2
MOVLW MS_PROG_EE_ADDR ;
MOVWF EEADRH ; MS Byte of Program Address to read
MOVLW LS_PROG_EE_ADDR ;
MOVWF EEADR ; LS Byte of Program Address to read
BSF STATUS, RP0 ; Bank 3
BSF EECON1, EEPGD ; Point to PROGRAM memory
BSF EECON1, RD ; EE Read
;
NOP
NOP ; Any instructions here are ignored as program
; memory is read in second cycle after BSF EECON1,RD
;
BCF STATUS, RP0 ; Bank 2
MOVF EEDATA, W ; W = LS Byte of Program EEDATA
MOVWF DATAL ;
MOVF EEDATH, W ; W = MS Byte of Program EEDATA
MOVWF DATAH ;
Required
Sequence

PIC16F87XA
3.6 Writing to Flash Program Memory
Flash program memory may only be written to if the
destination address is in a segment of memory that is
not write-protected, as defined in bits WRT1:WRT0 of
the device configuration word (Register 14-1). Flash
program memory must be written in four-word blocks. A
block consists of four words with sequential addresses,
with a lower boundary defined by an address, where
EEADR<1:0> = 00. At the same time, all block writes to
program memory are done as erase and write opera-tions.
The write operation is edge-aligned and cannot
occur across boundaries.
To write program data, it must first be loaded into the
buffer registers (see Figure 3-1). This is accomplished
by first writing the destination address to EEADR and
EEADRH and then writing the data to EEDATA and
EEDATH. After the address and data have been set up,
then the following sequence of events must be
executed:
1. Set the EEPGD control bit (EECON1<7>).
2. Write 55h, then AAh, to EECON2 (Flash
programming sequence).
3. Set the WR control bit (EECON1<1>).
All four buffer register locations MUST be written to with
correct data. If only one, two or three words are being
written to in the block of four words, then a read from
the program memory location(s) not being written to
must be performed. This takes the data from the pro-gram
location(s) not being written and loads it into the
EEDATA and EEDATH registers. Then the sequence of
events to transfer data to the buffer registers must be
executed.
To transfer data from the buffer registers to the program
memory, the EEADR and EEADRH must point to the last
location in the four-word block (EEADR<1:0> = 11).
Then the following sequence of events must be
executed:
1. Set the EEPGD control bit (EECON1<7>).
2. Write 55h, then AAh, to EECON2 (Flash
programming sequence).
3. Set control bit WR (EECON1<1>) to begin the
write operation.
The user must follow the same specific sequence to ini-tiate
the write for each word in the program block, writ-ing
each program word in sequence (00,01,10,11).
When the write is performed on the last word
(EEADR<1:0> = 11), the block of four words are
automatically erased and the contents of the buffer
registers are written into the program memory.
After the “BSF EECON1,WR” instruction, the processor
requires two cycles to set up the erase/write operation.
The user must place two NOP instructions after the WR
bit is set. Since data is being written to buffer registers,
the writing of the first three words of the block appears
to occur immediately. The processor will halt internal
operations for the typical 4 ms, only during the cycle in
which the erase takes place (i.e., the last word of the
four-word block). This is not Sleep mode as the clocks
and peripherals will continue to run. After the write
cycle, the processor will resume operation with the third
instruction after the EECON1 write instruction. If the
sequence is performed to any other location, the action
is ignored.
FIGURE 3-1: BLOCK WRITES TO FLASH PROGRAM MEMORY
7 5 0 7 0
EEDATH EEDATA
6 8
First word of block
to be written
Four words of
Flash are erased,
then all buffers
are transferred
to Flash
automatically
after this word
is written
14 14 14 14
EEADR<1:0> = 01
Buffer Register
EEADR<1:0> = 10
Buffer Register
Program Memory
EEADR<1:0> = 00
Buffer Register
EEADR<1:0> = 11
Buffer Register

PIC16F87XA
An example of the complete four-word write sequence
is shown in Example 3-4. The initial address is loaded
into the EEADRH:EEADR register pair; the four words
of data are loaded using indirect addressing.
EXAMPLE 3-4: WRITING TO FLASH PROGRAM MEMORY
; This write routine assumes the following:
;
; 1. A valid starting address (the least significant bits = ‘00’)is loaded in ADDRH:ADDRL
; 2. The 8 bytes of data are loaded, starting at the address in DATADDR
; 3. ADDRH, ADDRL and DATADDR are all located in shared data memory 0x70 - 0x7f
;
BSF STATUS,RP1 ;
MOVF ADDRH,W ; Load initial address
MOVWF EEADRH ;
MOVF ADDRL,W ;
MOVWF EEADR ;
MOVF DATAADDR,W ; Load initial data address
MOVWF FSR ;
LOOP MOVF INDF,W ; Load first data byte into lower
MOVWF EEDATA ;
INCF FSR,F ; Next byte
MOVF INDF,W ; Load second data byte into upper
MOVWF EEDATH ;
INCF FSR,F ;
BSF STATUS,RP0 ; Bank 3
BSF EECON1,EEPGD ; Point to program memory
BSF EECON1,WREN ; Enable writes
BCF INTCON,GIE ; Disable interrupts (if using)
MOVLW 55h ; Start of required write sequence:
MOVWF EECON2 ; Write 55h
MOVLW AAh ;
MOVWF EECON2 ; Write AAh
BSF EECON1,WR ; Set WR bit to begin write
NOP ; Any instructions here are ignored as processor
; halts to begin write sequence
NOP ; processor will stop here and wait for write complete
; after write processor continues with 3rd instruction
BCF EECON1,WREN ; Disable writes
BSF INTCON,GIE ; Enable interrupts (if using)
INCF EEADR,F ; Increment address
MOVF EEADR,W ; Check if lower two bits of address are ‘00’
ANDLW 0x03 ; Indicates when four words have been programmed
XORLW 0x03 ;
BTFSC STATUS,Z ; Exit if more than four words,
GOTO LOOP ; Continue if less than four words
Required
Sequence

PIC16F87XA
3.7 Protection Against Spurious Write
There are conditions when the device should not write
to the data EEPROM or Flash program memory. To
protect against spurious writes, various mechanisms
have been built-in. On power-up, WREN is cleared.
Also, the Power-up Timer (72 ms duration) prevents an
EEPROM write.
The write initiate sequence and the WREN bit together
help prevent an accidental write during brown-out,
power glitch or software malfunction.
3.8 Operation During Code-Protect
When the data EEPROM is code-protected, the micro-controller
can read and write to the EEPROM normally.
However, all external access to the EEPROM is
disabled. External write access to the program memory
is also disabled.
When program memory is code-protected, the microcon-troller
can read and write to program memory normally,
as well as execute instructions. Writes by the device may
be selectively inhibited to regions of the memory depend-ing
on the setting of bits WR1:WR0 of the configuration
word (see Section 14.1 “Configuration Bits” for addi-tional
information). External access to the memory is also
disabled.
TABLE 3-1: REGISTERS/BITS ASSOCIATED WITH DATA EEPROM AND
FLASH PROGRAM MEMORIES
Value on
Power-on
Reset
Value on
all other
Resets
10Ch EEDATA EEPROM/Flash Data Register Low Byte xxxx xxxx uuuu uuuu
10Dh EEADR EEPROM/Flash Address Register Low Byte xxxx xxxx uuuu uuuu
10Eh EEDATH — — EEPROM/Flash Data Register High Byte xxxx xxxx ---0 q000
10Fh EEADRH — — — EEPROM/Flash Address Register High Byte xxxx xxxx ---- ----
18Ch EECON1 EEPGD — — — WRERR WREN WR RD x--- x000 ---0 q000
18Dh EECON2 EEPROM Control Register 2 (not a physical register) ---- ---- ---- ----
0Dh PIR2 — CMIF — EEIF BCLIF — — CCP2IF -0-0 0--0 -0-0 0--0
8Dh PIE2 — CMIE — EEIE BCLIE — — CCP2IE -0-0 0--0 -0-0 0--0
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’, q = value depends upon condition.
Shaded cells are not used by data EEPROM or Flash program memory.

PIC16F87XA
NOTES:

PIC16F87XA
4.0 I/O PORTS
Some pins for these I/O ports are multiplexed with an
alternate function for the peripheral features on the
device. In general, when a peripheral is enabled, that
pin may not be used as a general purpose I/O pin.
Additional information on I/O ports may be found in the
PICmicro™ Mid-Range Reference Manual (DS33023).
4.1 PORTA and the TRISA Register
PORTA is a 6-bit wide, bidirectional port. The corre-sponding
data direction register is TRISA. Setting a
TRISA bit (= 1) will make the corresponding PORTA pin
an input (i.e., put the corresponding output driver in a
High-Impedance mode). Clearing a TRISA bit (= 0) will
make the corresponding PORTA pin an output (i.e., put
the contents of the output latch on the selected pin).
Reading the PORTA register reads the status of the
pins, whereas writing to it will write to the port latch. All
write operations are read-modify-write operations.
Therefore, a write to a port implies that the port pins are
read, the value is modified and then written to the port
data latch.
Pin RA4 is multiplexed with the Timer0 module clock
input to become the RA4/T0CKI pin. The RA4/T0CKI
pin is a Schmitt Trigger input and an open-drain output.
All other PORTA pins have TTL input levels and full
CMOS output drivers.
Other PORTA pins are multiplexed with analog inputs
and the analog VREF input for both the A/D converters
and the comparators. The operation of each pin is
selected by clearing/setting the appropriate control bits
in the ADCON1 and/or CMCON registers.
Note: On a Power-on Reset, these pins are con-figured
as analog inputs and read as ‘0’.
The comparators are in the off (digital)
state.
The TRISA register controls the direction of the port
pins even when they are being used as analog inputs.
The user must ensure the bits in the TRISA register are
maintained set when using them as analog inputs.
EXAMPLE 4-1: INITIALIZING PORTA
BCF STATUS, RP0 ;
BCF STATUS, RP1 ; Bank0
CLRF PORTA ; Initialize PORTA by
; clearing output
; data latches
BSF STATUS, RP0 ; Select Bank 1
MOVLW 0x06 ; Configure all pins
MOVWF ADCON1 ; as digital inputs
MOVLW 0xCF ; Value used to
; initialize data
; direction
MOVWF TRISA ; Set RA<3:0> as inputs
; RA<5:4> as outputs
; TRISA<7:6>are always
; read as '0'.
FIGURE 4-1: BLOCK DIAGRAM OF
RA3:RA0 PINS
Data
Bus
Data Latch
D Q
CK Q
TRIS Latch
D Q
CK Q
Analog
Input
Mode
Q D
EN
VDD
P
N
WR
PORTA
WR
TRISA
RD
TRISA
RD PORTA
VSS
I/O pin(1)
TTL
Input
Buffer
To A/D Converter or Comparator
Note 1: I/O pins have protection diodes to VDD and VSS.

PIC16F87XA
FIGURE 4-2: BLOCK DIAGRAM OF RA4/T0CKI PIN
CMCON<2:0> = x01 or 011
C1OUT
Data Bus
WR PORTA
WR TRISA
RD TRISA
RD PORTA
Data Latch
D Q
CK Q
TRIS Latch
TMR0 Clock Input
D Q
CK Q
1
0
Note 1: I/O pin has protection diodes to VSS only.
FIGURE 4-3: BLOCK DIAGRAM OF RA5 PIN
N
VSS
Schmitt
Trigger
Input
Buffer
I/O pin(1)
Q D
EN
EN
CMCON<2:0> = 011 or 101
C2OUT
Data Bus
WR PORTA
WR TRISA
RD TRISA
RD PORTA
Data Latch
D Q
CK Q
TRIS Latch
I/O pin(1)
TTL
Input
Buffer
D Q
CK Q
A/D Converter or SS Input
VDD
P
N
VSS
Q D
EN
EN
1
0
Note 1: I/O pin has protection diodes to VDD and VSS.
Analog
IIP Mode

PIC16F87XA
TABLE 4-1: PORTA FUNCTIONS
Name Bit# Buffer Function
RA0/AN0 bit 0 TTL Input/output or analog input.
RA1/AN1 bit 1 TTL Input/output or analog input.
RA2/AN2/VREF-/CVREF bit 2 TTL Input/output or analog input or VREF- or CVREF.
RA3/AN3/VREF+ bit 3 TTL Input/output or analog input or VREF+.
RA4/T0CKI/C1OUT bit 4 ST Input/output or external clock input for Timer0 or comparator output.
Output is open-drain type.
RA5/AN4/SS/C2OUT bit 5 TTL Input/output or analog input or slave select input for synchronous serial
port or comparator output.
Legend: TTL = TTL input, ST = Schmitt Trigger input
TABLE 4-2: SUMMARY OF REGISTERS ASSOCIATED WITH PORTA
Value on:
POR, BOR
Value on
all other
Resets
05h PORTA — — RA5 RA4 RA3 RA2 RA1 RA0 --0x 0000 --0u 0000
85h TRISA — — PORTA Data Direction Register --11 1111 --11 1111
9Ch CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 0000 0111 0000 0111
9Dh CVRCON CVREN CVROE CVRR — CVR3 CVR2 CVR1 CVR0 000- 0000 000- 0000
9Fh ADCON1 ADFM ADCS2 — — PCFG3 PCFG2 PCFG1 PCFG0 00-- 0000 00-- 0000
Legend: x = unknown, u = unchanged, - = unimplemented locations read as ‘0’. Shaded cells are not used by PORTA.
Note: When using the SSP module in SPI Slave mode and SS enabled, the A/D converter must be set to one of
the following modes, where PCFG3:PCFG0 = 0100, 0101, 011x, 1101, 1110, 1111.

PIC16F87XA
4.2 PORTB and the TRISB Register
PORTB is an 8-bit wide, bidirectional port. The corre-sponding
data direction register is TRISB. Setting a
TRISB bit (= 1) will make the corresponding PORTB
pin an input (i.e., put the corresponding output driver in
a High-Impedance mode). Clearing a TRISB bit (= 0)
will make the corresponding PORTB pin an output (i.e.,
put the contents of the output latch on the selected pin).
Three pins of PORTB are multiplexed with the In-Circuit
Debugger and Low-Voltage Programming function:
RB3/PGM, RB6/PGC and RB7/PGD. The alternate
functions of these pins are described in Section 14.0
“Special Features of the CPU”.
Each of the PORTB pins has a weak internal pull-up. A
single control bit can turn on all the pull-ups. This is per-formed
by clearing bit RBPU (OPTION_REG<7>). The
weak pull-up is automatically turned off when the port
pin is configured as an output. The pull-ups are
disabled on a Power-on Reset.
RB3:RB0 PINS
Data Latch
RBPU(2)
VDD
P
D Q
CK
TRIS Latch
D Q
CK
TTL
Input
Buffer
Q D
EN
Data Bus
WR Port
WR TRIS
RD TRIS
RD Port
Weak
Pull-up
I/O pin(1)
RD Port
RB0/INT
Schmitt Trigger
Buffer
RB3/PGM
Note 1: I/O pins have diode protection to VDD and VSS.
2: To enable weak pull-ups, set the appropriate TRIS
bit(s) and clear the RBPU bit (OPTION_REG<7>).
Four of the PORTB pins, RB7:RB4, have an interrupt-on-
change feature. Only pins configured as inputs can
cause this interrupt to occur (i.e., any RB7:RB4 pin
configured as an output is excluded from the interrupt-on-
change comparison). The input pins (of RB7:RB4)
are compared with the old value latched on the last
read of PORTB. The “mismatch” outputs of RB7:RB4
are OR’ed together to generate the RB port change
interrupt with flag bit RBIF (INTCON<0>).
This interrupt can wake the device from Sleep. The
user, in the Interrupt Service Routine, can clear the
interrupt in the following manner:
a) Any read or write of PORTB. This will end the
mismatch condition.
b) Clear flag bit RBIF.
A mismatch condition will continue to set flag bit RBIF.
Reading PORTB will end the mismatch condition and
allow flag bit RBIF to be cleared.
The interrupt-on-change feature is recommended for
wake-up on key depression operation and operations
where PORTB is only used for the interrupt-on-change
feature. Polling of PORTB is not recommended while
using the interrupt-on-change feature.
This interrupt-on-mismatch feature, together with soft-ware
configurable pull-ups on these four pins, allow
easy interface to a keypad and make it possible for
wake-up on key depression. Refer to the application
note, AN552, “Implementing Wake-up on Key Stroke”
(DS00552).
RB0/INT is an external interrupt input pin and is
configured using the INTEDG bit (OPTION_REG<6>).
RB0/INT is discussed in detail in Section 14.11.1 “INT
Interrupt”.
RB7:RB4 PINS
Data Latch
RBPU(2)
Data Bus
WR Port
WR TRIS
RD TRIS
RD Port
Set RBIF
From other
VDD
P
Weak
Pull-up
I/O pin(1)
D Q
CK
TRIS Latch
D Q
CK
Latch
TTL
Input
Buffer ST
Q D
EN
Q D
EN
RB7:RB4 pins
Buffer
Q1
RD Port
RB7:RB6
Q3
In Serial Programming Mode
2: To enable weak pull-ups, set the appropriate TRIS
bit(s) and clear the RBPU bit (OPTION_REG<7>).

PIC16F87XA
TABLE 4-3: PORTB FUNCTIONS
Name Bit# Buffer Function
RB0/INT bit 0 TTL/ST(1) Input/output pin or external interrupt input. Internal software programmable
weak pull-up.
RB1 bit 1 TTL Input/output pin. Internal software programmable weak pull-up.
RB2 bit 2 TTL Input/output pin. Internal software programmable weak pull-up.
RB3/PGM(3) bit 3 TTL Input/output pin or programming pin in LVP mode. Internal software
programmable weak pull-up.
RB4 bit 4 TTL Input/output pin (with interrupt-on-change). Internal software programmable
weak pull-up.
RB5 bit 5 TTL Input/output pin (with interrupt-on-change). Internal software programmable
weak pull-up.
RB6/PGC bit 6 TTL/ST(2) Input/output pin (with interrupt-on-change) or in-circuit debugger pin.
Internal software programmable weak pull-up. Serial programming clock.
RB7/PGD bit 7 TTL/ST(2) Input/output pin (with interrupt-on-change) or in-circuit debugger pin.
Internal software programmable weak pull-up. Serial programming data.
Legend: TTL = TTL input, ST = Schmitt Trigger input
2: This buffer is a Schmitt Trigger input when used in Serial Programming mode or in-circuit debugger.
3: Low-Voltage ICSP Programming (LVP) is enabled by default which disables the RB3 I/O function. LVP
must be disabled to enable RB3 as an I/O pin and allow maximum compatibility to the other 28-pin and
40-pin mid-range devices.
TABLE 4-4: SUMMARY OF REGISTERS ASSOCIATED WITH PORTB
Value on:
POR, BOR
Value on
all other
Resets
06h, 106h PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 xxxx xxxx uuuu uuuu
86h, 186h TRISB PORTB Data Direction Register 1111 1111 1111 1111
81h, 181h OPTION_REG RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0 1111 1111 1111 1111
Legend: x = unknown, u = unchanged. Shaded cells are not used by PORTB.

PIC16F87XA
4.3 PORTC and the TRISC Register
PORTC is an 8-bit wide, bidirectional port. The corre-sponding
data direction register is TRISC. Setting a
TRISC bit (= 1) will make the corresponding PORTC
pin an input (i.e., put the corresponding output driver in
a High-Impedance mode). Clearing a TRISC bit (= 0)
will make the corresponding PORTC pin an output (i.e.,
put the contents of the output latch on the selected pin).
PORTC is multiplexed with several peripheral functions
(Table 4-5). PORTC pins have Schmitt Trigger input
buffers.
When the I2C module is enabled, the PORTC<4:3>
pins can be configured with normal I2C levels, or with
SMBus levels, by using the CKE bit (SSPSTAT<6>).
When enabling peripheral functions, care should be
taken in defining TRIS bits for each PORTC pin. Some
peripherals override the TRIS bit to make a pin an
output, while other peripherals override the TRIS bit to
make a pin an input. Since the TRIS bit override is in
effect while the peripheral is enabled, read-modify-write
instructions (BSF, BCF, XORWF) with TRISC as the
destination, should be avoided. The user should refer
to the corresponding peripheral section for the correct
TRIS bit settings.
FIGURE 4-6: PORTC BLOCK DIAGRAM
(PERIPHERAL OUTPUT
OVERRIDE) RC<2:0>,
RC<7:5>
FIGURE 4-7: PORTC BLOCK DIAGRAM
(PERIPHERAL OUTPUT
OVERRIDE) RC<4:3>
Port/Peripheral Select(2)
Peripheral Data Out
Data Bus
WR Port
WR TRIS
D Q
CK Q
Data Latch
D Q
CK Q
TRIS Latch
VDD
VSS
Schmitt
Trigger
Q D
EN
0
1
P
N
RD TRIS
Peripheral
OE(3)
RD Port
Peripheral Input
I/O
pin(1)
2: Port/Peripheral Select signal selects between port
data and peripheral output.
3: Peripheral OE (Output Enable) is only activated if
Peripheral Select is active.
Port/Peripheral Select(2)
Peripheral Data Out
Data Bus
WR Port
WR TRIS
D Q
CK Q
Data Latch
D Q
CK Q
TRIS Latch
VDD
N
VSS
Schmitt
Trigger
Q D
EN
0
1
P
RD TRIS
Peripheral
OE(3)
RD Port
SSP Input
I/O
pin(1)
0
1
CKE
SSPSTAT<6>
Schmitt
Trigger
with
SMBus
Levels
2: Port/Peripheral Select signal selects between port data
and peripheral output.
3: Peripheral OE (Output Enable) is only activated if
Peripheral Select is active.

PIC16F87XA
TABLE 4-5: PORTC FUNCTIONS
Name Bit# Buffer Type Function
RC0/T1OSO/T1CKI bit 0 ST Input/output port pin or Timer1 oscillator output/Timer1 clock input.
RC1/T1OSI/CCP2 bit 1 ST Input/output port pin or Timer1 oscillator input or Capture2 input/
Compare2 output/PWM2 output.
RC2/CCP1 bit 2 ST Input/output port pin or Capture1 input/Compare1 output/
PWM1 output.
RC3/SCK/SCL bit 3 ST RC3 can also be the synchronous serial clock for both SPI and
I2C modes.
RC4/SDI/SDA bit 4 ST RC4 can also be the SPI data in (SPI mode) or data I/O (I2C mode).
RC5/SDO bit 5 ST Input/output port pin or Synchronous Serial Port data output.
RC6/TX/CK bit 6 ST Input/output port pin or USART asynchronous transmit or
synchronous clock.
RC7/RX/DT bit 7 ST Input/output port pin or USART asynchronous receive or
synchronous data.
Legend: ST = Schmitt Trigger input
TABLE 4-6: SUMMARY OF REGISTERS ASSOCIATED WITH PORTC
Value on:
POR, BOR
Value on
all other
Resets
07h PORTC RC7 RC6 RC5 RC4 RC3 RC2 RC1 RC0 xxxx xxxx uuuu uuuu
87h TRISC PORTC Data Direction Register 1111 1111 1111 1111
Legend: x = unknown, u = unchanged

PIC16F87XA
4.4 PORTD and TRISD Registers
Note: PORTD and TRISD are not implemented
on the 28-pin devices. Data
PORTD is an 8-bit port with Schmitt Trigger input
buffers. Each pin is individually configurable as an input
or output.
PORTD can be configured as an 8-bit wide
microprocessor port (Parallel Slave Port) by setting
control bit, PSPMODE (TRISE<4>). In this mode, the
input buffers are TTL.
FIGURE 4-8: PORTD BLOCK DIAGRAM
(IN I/O PORT MODE)
TABLE 4-7: PORTD FUNCTIONS
Bus
WR
Port
WR
TRIS
RD
TRIS
RD Port
Data Latch
D Q
CK
TRIS Latch
D Q
CK
Q D
EN
EN
RD0/PSP0 bit 0 ST/TTL(1) Input/output port pin or Parallel Slave Port bit 0.
RD2/PSP2 bit2 ST/TTL(1) Input/output port pin or Parallel Slave Port bit 2.
Legend: ST = Schmitt Trigger input, TTL = TTL input
Note 1: Input buffers are Schmitt Triggers when in I/O mode and TTL buffers when in Parallel Slave Port mode.
TABLE 4-8: SUMMARY OF REGISTERS ASSOCIATED WITH PORTD
Schmitt
Trigger
Input
Buffer
I/O pin(1)
Value on:
POR, BOR
Value on
all other
Resets
08h PORTD RD7 RD6 RD5 RD4 RD3 RD2 RD1 RD0 xxxx xxxx uuuu uuuu
88h TRISD PORTD Data Direction Register 1111 1111 1111 1111
89h TRISE IBF OBF IBOV PSPMODE — PORTE Data Direction Bits 0000 -111 0000 -111
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are not used by PORTD.

PIC16F87XA
4.5 PORTE and TRISE Register
Note: PORTE and TRISE are not implemented
on the 28-pin devices.
PORTE has three pins (RE0/RD/AN5, RE1/WR/AN6
and RE2/CS/AN7) which are individually configurable
as inputs or outputs. These pins have Schmitt Trigger
input buffers.
The PORTE pins become the I/O control inputs for the
microprocessor port when bit PSPMODE (TRISE<4>) is
set. In this mode, the user must make certain that the
TRISE<2:0> bits are set and that the pins are configured
as digital inputs. Also, ensure that ADCON1 is config-ured
for digital I/O. In this mode, the input buffers are
TTL.
Register 4-1 shows the TRISE register which also
controls the Parallel Slave Port operation.
PORTE pins are multiplexed with analog inputs. When
selected for analog input, these pins will read as ‘0’s.
TRISE controls the direction of the RE pins, even when
they are being used as analog inputs. The user must
make sure to keep the pins configured as inputs when
using them as analog inputs.
FIGURE 4-9: PORTE BLOCK DIAGRAM
(IN I/O PORT MODE)
Note: On a Power-on Reset, these pins are
configured as analog inputs and read as ‘0’.
TABLE 4-9: PORTE FUNCTIONS
Data
Bus
WR
Port
WR
TRIS
RD
TRIS
RD Port
Data Latch
D Q
CK
TRIS Latch
Schmitt
Trigger
Input
Buffer
D Q
CK
Q D
EN
EN
I/O pin(1)
RE0/RD/AN5 bit 0 ST/TTL(1)
I/O port pin or read control input in Parallel Slave Port mode or analog input:
RD
1 = Idle
0 = Read operation. Contents of PORTD register are output to PORTD
I/O pins (if chip selected).
RE1/WR/AN6 bit 1 ST/TTL(1)
I/O port pin or write control input in Parallel Slave Port mode or analog input:
WR
1 = Idle
0 = Write operation. Value of PORTD I/O pins is latched into PORTD
register (if chip selected).
RE2/CS/AN7 bit 2 ST/TTL(1)
I/O port pin or chip select control input in Parallel Slave Port mode or analog input:
CS
1 = Device is not selected
0 = Device is selected
Legend: ST = Schmitt Trigger input, TTL = TTL input
Note 1: Input buffers are Schmitt Triggers when in I/O mode and TTL buffers when in Parallel Slave Port mode.

PIC16F87XA
TABLE 4-10: SUMMARY OF REGISTERS ASSOCIATED WITH PORTE
09h PORTE — — — — — RE2 RE1 RE0 ---- -xxx ---- -uuu
89h TRISE IBF OBF IBOV PSPMODE — PORTE Data Direction bits 0000 -111 0000 -111
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are not used by PORTE.
REGISTER 4-1: TRISE REGISTER (ADDRESS 89h)
Value on:
POR, BOR
Value on
all other
Resets
R-0 R-0 R/W-0 R/W-0 U-0 R/W-1 R/W-1 R/W-1
IBF OBF IBOV PSPMODE — Bit 2 Bit 1 Bit 0
bit 7 bit 0
Parallel Slave Port Status/Control Bits:
bit 7 IBF: Input Buffer Full Status bit
1 = A word has been received and is waiting to be read by the CPU
0 = No word has been received
bit 6 OBF: Output Buffer Full Status bit
1 = The output buffer still holds a previously written word
0 = The output buffer has been read
bit 5 IBOV: Input Buffer Overflow Detect bit (in Microprocessor mode)
1 = A write occurred when a previously input word has not been read (must be cleared in
software)
0 = No overflow occurred
bit 4 PSPMODE: Parallel Slave Port Mode Select bit
1 = PORTD functions in Parallel Slave Port mode
0 = PORTD functions in general purpose I/O mode
PORTE Data Direction Bits:
bit 2 Bit 2: Direction Control bit for pin RE2/CS/AN7
1 = Input
0 = Output
bit 1 Bit 1: Direction Control bit for pin RE1/WR/AN6
1 = Input
0 = Output
bit 0 Bit 0: Direction Control bit for pin RE0/RD/AN5
1 = Input
0 = Output
Legend:

PIC16F87XA
4.6 Parallel Slave Port
The Parallel Slave Port (PSP) is not implemented on
the PIC16F873A or PIC16F876A.
PORTD operates as an 8-bit wide Parallel Slave Port,
or microprocessor port, when control bit PSPMODE
(TRISE<4>) is set. In Slave mode, it is asynchronously
readable and writable by the external world through RD
control input pin, RE0/RD/AN5, and WR control input
pin, RE1/WR/AN6.
The PSP can directly interface to an 8-bit
microprocessor data bus. The external microprocessor
can read or write the PORTD latch as an 8-bit latch.
Setting bit PSPMODE enables port pin RE0/RD/AN5 to
be the RD input, RE1/WR/AN6 to be the WR input and
RE2/CS/AN7 to be the CS (Chip Select) input. For this
functionality, the corresponding data direction bits of
the TRISE register (TRISE<2:0>) must be configured
as inputs (set). The A/D port configuration bits,
PCFG3:PCFG0 (ADCON1<3:0>), must be set to
configure pins RE2:RE0 as digital I/O.
There are actually two 8-bit latches: one for data output
and one for data input. The user writes 8-bit data to the
PORTD data latch and reads data from the port pin
latch (note that they have the same address). In this
mode, the TRISD register is ignored since the external
device is controlling the direction of data flow.
A write to the PSP occurs when both the CS and WR
lines are first detected low. When either the CS or WR
lines become high (level triggered), the Input Buffer Full
(IBF) status flag bit (TRISE<7>) is set on the Q4 clock
cycle, following the next Q2 cycle, to signal the write is
complete (Figure 4-11). The interrupt flag bit, PSPIF
(PIR1<7>), is also set on the same Q4 clock cycle. IBF
can only be cleared by reading the PORTD input latch.
The Input Buffer Overflow (IBOV) status flag bit
(TRISE<5>) is set if a second write to the PSP is
attempted when the previous byte has not been read
out of the buffer.
A read from the PSP occurs when both the CS and RD
lines are first detected low. The Output Buffer Full
(OBF) status flag bit (TRISE<6>) is cleared
immediately (Figure 4-12), indicating that the PORTD
latch is waiting to be read by the external bus. When
either the CS or RD pin becomes high (level triggered),
the interrupt flag bit PSPIF is set on the Q4 clock cycle,
following the next Q2 cycle, indicating that the read is
complete. OBF remains low until data is written to
PORTD by the user firmware.
When not in PSP mode, the IBF and OBF bits are held
clear. However, if flag bit IBOV was previously set, it
must be cleared in firmware.
An interrupt is generated and latched into flag bit
PSPIF when a read or write operation is completed.
PSPIF must be cleared by the user in firmware and the
interrupt can be disabled by clearing the interrupt
enable bit PSPIE (PIE1<7>).
FIGURE 4-10: PORTD AND PORTE
BLOCK DIAGRAM
(PARALLEL SLAVE PORT)
Data Bus
WR
Port
RD Port
RDx pin
D Q
CK
Q D
EN
EN
One bit of PORTD
Set Interrupt Flag
PSPIF (PIR1<7>)
TTL
Read
TTL
Chip Select
Write
RD
CS
WR
TTL
TTL

PIC16F87XA
FIGURE 4-11: PARALLEL SLAVE PORT WRITE WAVEFORMS
Q1 Q2 Q3 Q4
CS
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
WR
RD
PORTD<7:0>
IBF
OBF
PSPIF
FIGURE 4-12: PARALLEL SLAVE PORT READ WAVEFORMS
Q1 Q2 Q3 Q4
CS
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
WR
RD
PORTD<7:0>
IBF
OBF
PSPIF
TABLE 4-11: REGISTERS ASSOCIATED WITH PARALLEL SLAVE PORT
Value on:
POR, BOR
Value on
all other
Resets
08h PORTD Port Data Latch when written; Port pins when read xxxx xxxx uuuu uuuu
09h PORTE — — — — — RE2 RE1 RE0 ---- -xxx ---- -uuu
89h TRISE IBF OBF IBOV PSPMODE — PORTE Data Direction bits 0000 -111 0000 -111
0Ch PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 0000 0000
8Ch PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 0000 0000 0000 0000
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are not used by the Parallel Slave Port.
Note 1: Bits PSPIE and PSPIF are reserved on the PIC16F873A/876A; always maintain these bits clear.

PIC16F87XA
5.0 TIMER0 MODULE
The Timer0 module timer/counter has the following
features:
• 8-bit timer/counter
• Readable and writable
• 8-bit software programmable prescaler
• Internal or external clock select
• Interrupt on overflow from FFh to 00h
• Edge select for external clock
Figure 5-1 is a block diagram of the Timer0 module and
the prescaler shared with the WDT.
Additional information on the Timer0 module is
available in the PICmicro® Mid-Range MCU Family
Reference Manual (DS33023).
Timer mode is selected by clearing bit T0CS
(OPTION_REG<5>). In Timer mode, the Timer0
module will increment every instruction cycle (without
prescaler). If the TMR0 register is written, the incre-ment
is inhibited for the following two instruction cycles.
The user can work around this by writing an adjusted
value to the TMR0 register.
Counter mode is selected by setting bit T0CS
(OPTION_REG<5>). In Counter mode, Timer0 will
increment either on every rising or falling edge of pin
RA4/T0CKI. The incrementing edge is determined by
the Timer0 Source Edge Select bit, T0SE
(OPTION_REG<4>). Clearing bit T0SE selects the ris-ing
edge. Restrictions on the external clock input are
discussed in detail in Section 5.2 “Using Timer0 with
an External Clock”.
The prescaler is mutually exclusively shared between
the Timer0 module and the Watchdog Timer. The
prescaler is not readable or writable. Section 5.3
“Prescaler” details the operation of the prescaler.
5.1 Timer0 Interrupt
The TMR0 interrupt is generated when the TMR0
register overflows from FFh to 00h. This overflow sets
bit TMR0IF (INTCON<2>). The interrupt can be
masked by clearing bit TMR0IE (INTCON<5>). Bit
TMR0IF must be cleared in software by the Timer0
module Interrupt Service Routine before re-enabling
this interrupt. The TMR0 interrupt cannot awaken the
processor from Sleep since the timer is shut-off during
Sleep.
FIGURE 5-1: BLOCK DIAGRAM OF THE TIMER0/WDT PRESCALER
CLKO (= FOSC/4)
RA4/T0CKI
T0SE
pin
M
UX
Sync
2
Cycles
Data Bus
8
TMR0 Reg
1
1 0
PRESCALER
8-bit Prescaler
8
8-to-1 MUX
M
UX
0 1
MUX
Watchdog
Timer
PSA
0
1
WDT
Time-out
PS2:PS0
WDT Enable bit
0
PSA
T0CS
Note: T0CS, T0SE, PSA, PS2:PS0 are (OPTION_REG<5:0>).
PSA
M
UX
Set Flag bit TMR0IF
on Overflow

PIC16F87XA
5.2 Using Timer0 with an External
Clock
When no prescaler is used, the external clock input is
the same as the prescaler output. The synchronization
of T0CKI with the internal phase clocks is accom-plished
by sampling the prescaler output on the Q2 and
Q4 cycles of the internal phase clocks. Therefore, it is
necessary for T0CKI to be high for at least 2 TOSC (and
a small RC delay of 20 ns) and low for at least 2 TOSC
(and a small RC delay of 20 ns). Refer to the electrical
specification of the desired device.
5.3 Prescaler
There is only one prescaler available which is mutually
exclusively shared between the Timer0 module and the
Watchdog Timer. A prescaler assignment for the
Timer0 module means that there is no prescaler for the
Watchdog Timer and vice versa. This prescaler is not
readable or writable (see Figure 5-1).
The PSA and PS2:PS0 bits (OPTION_REG<3:0>)
determine the prescaler assignment and prescale ratio.
When assigned to the Timer0 module, all instructions
writing to the TMR0 register (e.g., CLRF 1, MOVWF 1,
BSF 1,x....etc.) will clear the prescaler. When assigned
to WDT, a CLRWDT instruction will clear the prescaler
along with the Watchdog Timer. The prescaler is not
readable or writable.
REGISTER 5-1: OPTION_REG REGISTER
Note: Writing to TMR0 when the prescaler is
assigned to Timer0 will clear the prescaler
count, but will not change the prescaler
assignment.
RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0
bit 7 bit 0
bit 7 RBPU
bit 6 INTEDG
bit 5 T0CS: TMR0 Clock Source Select bit
1 = Transition on T0CKI pin
0 = Internal instruction cycle clock (CLKO)
bit 4 T0SE: TMR0 Source Edge Select bit
1 = Increment on high-to-low transition on T0CKI pin
0 = Increment on low-to-high transition on T0CKI pin
bit 3 PSA: Prescaler Assignment bit
1 = Prescaler is assigned to the WDT
0 = Prescaler is assigned to the Timer0 module
bit 2-0 PS2:PS0: Prescaler Rate Select bits
Bit Value TMR0 Rate WDT Rate
000
001
010
011
100
101
110
111
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
1 : 1
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
Legend:
Note: To avoid an unintended device Reset, the instruction sequence shown in the
PICmicro® Mid-Range MCU Family Reference Manual (DS33023) must be exe-cuted
when changing the prescaler assignment from Timer0 to the WDT. This
sequence must be followed even if the WDT is disabled.

PIC16F87XA
TABLE 5-1: REGISTERS ASSOCIATED WITH TIMER0
Value on:
POR, BOR
Value on
all other
Resets
01h,101h TMR0 Timer0 Module Register xxxx xxxx uuuu uuuu
0Bh,8Bh,
INTCON GIE PEIE TMR0IE INTE RBIE TMR0IF INTF RBIF 0000 000x 0000 000u
10Bh,18Bh
81h,181h OPTION_REG RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0 1111 1111 1111 1111
Legend: x = unknown, u = unchanged, - = unimplemented locations read as ‘0’. Shaded cells are not used by Timer0.

PIC16F87XA
NOTES:

PIC16F87XA
6.0 TIMER1 MODULE
The Timer1 module is a 16-bit timer/counter consisting
of two 8-bit registers (TMR1H and TMR1L) which are
readable and writable. The TMR1 register pair
(TMR1H:TMR1L) increments from 0000h to FFFFh
and rolls over to 0000h. The TMR1 interrupt, if enabled,
is generated on overflow which is latched in interrupt
flag bit, TMR1IF (PIR1<0>). This interrupt can be
enabled/disabled by setting/clearing TMR1 interrupt
enable bit, TMR1IE (PIE1<0>).
Timer1 can operate in one of two modes:
• As a Timer
• As a Counter
The operating mode is determined by the clock select
bit, TMR1CS (T1CON<1>).
In Timer mode, Timer1 increments every instruction
cycle. In Counter mode, it increments on every rising
edge of the external clock input.
Timer1 can be enabled/disabled by setting/clearing
control bit, TMR1ON (T1CON<0>).
Timer1 also has an internal “Reset input”. This Reset
can be generated by either of the two CCP modules
(Section 8.0 “Capture/Compare/PWM Modules”).
Register 6-1 shows the Timer1 Control register.
When the Timer1 oscillator is enabled (T1OSCEN is
set), the RC1/T1OSI/CCP2 and RC0/T1OSO/T1CKI
pins become inputs. That is, the TRISC<1:0> value is
ignored and these pins read as ‘0’.
Additional information on timer modules is available in
the PICmicro® Mid-Range MCU Family Reference
Manual (DS33023).
REGISTER 6-1: T1CON: TIMER1 CONTROL REGISTER (ADDRESS 10h)
U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
— — T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON
bit 7 bit 0
bit 5-4 T1CKPS1:T1CKPS0: Timer1 Input Clock Prescale Select bits
11 = 1:8 prescale value
bit 3 T1OSCEN: Timer1 Oscillator Enable Control bit
1 = Oscillator is enabled
0 = Oscillator is shut-off (the oscillator inverter is turned off to eliminate power drain)
bit 2 T1SYNC: Timer1 External Clock Input Synchronization Control bit
When TMR1CS = 1:
1 = Do not synchronize external clock input
0 = Synchronize external clock input
When TMR1CS = 0:
This bit is ignored. Timer1 uses the internal clock when TMR1CS = 0.
bit 1 TMR1CS: Timer1 Clock Source Select bit
1 = External clock from pin RC0/T1OSO/T1CKI (on the rising edge)
0 = Internal clock (FOSC/4)
bit 0 TMR1ON: Timer1 On bit
1 = Enables Timer1
0 = Stops Timer1
Legend:

PIC16F87XA
6.1 Timer1 Operation in Timer Mode
Timer mode is selected by clearing the TMR1CS
(T1CON<1>) bit. In this mode, the input clock to the
timer is FOSC/4. The synchronize control bit, T1SYNC
(T1CON<2>), has no effect since the internal clock is
always in sync.
6.2 Timer1 Counter Operation
Timer1 may operate in either a Synchronous, or an
Asynchronous mode, depending on the setting of the
TMR1CS bit.
When Timer1 is being incremented via an external
source, increments occur on a rising edge. After Timer1
is enabled in Counter mode, the module must first have
a falling edge before the counter begins to increment.
FIGURE 6-1: TIMER1 INCREMENTING EDGE
T1CKI
(Default High)
T1CKI
(Default Low)
Note: Arrows indicate counter increments.
6.3 Timer1 Operation in Synchronized
Counter Mode
Counter mode is selected by setting bit TMR1CS. In
this mode, the timer increments on every rising edge of
clock input on pin RC1/T1OSI/CCP2 when bit
T1OSCEN is set, or on pin RC0/T1OSO/T1CKI when
bit T1OSCEN is cleared.
If T1SYNC is cleared, then the external clock input is
synchronized with internal phase clocks. The synchro-nization
is done after the prescaler stage. The
prescaler stage is an asynchronous ripple counter.
In this configuration, during Sleep mode, Timer1 will not
increment even if the external clock is present since the
synchronization circuit is shut-off. The prescaler,
however, will continue to increment.
FIGURE 6-2: TIMER1 BLOCK DIAGRAM
TMR1
TMR1H TMR1L
T1OSC
0
1
T1SYNC
Prescaler
1, 2, 4, 8
2
T1CKPS1:T1CKPS0
TMR1ON
On/Off
1
0
TMR1CS
Synchronized
Clock Input
Synchronize
det
Q Clock
T1OSCEN
Enable
Oscillator(1)
FOSC/4
Internal
Clock
Set Flag bit
TMR1IF on
Overflow
RC0/T1OSO/T1CKI
RC1/T1OSI/CCP2(2)
Note 1: When the T1OSCEN bit is cleared, the inverter is turned off. This eliminates power drain.

PIC16F87XA
6.4 Timer1 Operation in
Asynchronous Counter Mode
If control bit T1SYNC (T1CON<2>) is set, the external
clock input is not synchronized. The timer continues to
increment asynchronous to the internal phase clocks.
The timer will continue to run during Sleep and can
generate an interrupt-on-overflow which will wake-up
the processor. However, special precautions in
software are needed to read/write the timer.
In Asynchronous Counter mode, Timer1 cannot be
used as a time base for capture or compare operations.
6.4.1 READING AND WRITING TIMER1 IN
ASYNCHRONOUS COUNTER MODE
Reading TMR1H or TMR1L while the timer is running
from an external asynchronous clock will ensure a valid
read (taken care of in hardware). However, the user
should keep in mind that reading the 16-bit timer in two
8-bit values itself, poses certain problems, since the
timer may overflow between the reads.
For writes, it is recommended that the user simply stop
the timer and write the desired values. A write conten-tion
may occur by writing to the timer registers while the
register is incrementing. This may produce an
unpredictable value in the timer register.
Reading the 16-bit value requires some care.
Examples 12-2 and 12-3 in the PICmicro® Mid-Range
MCU Family Reference Manual (DS33023) show how
to read and write Timer1 when it is running in
Asynchronous mode.
6.5 Timer1 Oscillator
A crystal oscillator circuit is built-in between pins T1OSI
(input) and T1OSO (amplifier output). It is enabled by
setting control bit, T1OSCEN (T1CON<3>). The oscil-lator
is a low-power oscillator, rated up to 200 kHz. It
will continue to run during Sleep. It is primarily intended
for use with a 32 kHz crystal. Table 6-1 shows the
capacitor selection for the Timer1 oscillator.
The Timer1 oscillator is identical to the LP oscillator.
The user must provide a software time delay to ensure
proper oscillator start-up.
TABLE 6-1: CAPACITOR SELECTION FOR
THE TIMER1 OSCILLATOR
Osc Type Freq. C1 C2
LP 32 kHz 33 pF 33 pF
100 kHz 15 pF 15 pF
200 kHz 15 pF 15 pF
These values are for design guidance only.
Crystals Tested:
32.768 kHz Epson C-001R32.768K-A ± 20 PPM
100 kHz Epson C-2 100.00 KC-P ± 20 PPM
200 kHz STD XTL 200.000 kHz ± 20 PPM
Note 1: Higher capacitance increases the stability
of oscillator but also increases the start-up
time.
2: Since each resonator/crystal has its own
characteristics, the user should consult
the resonator/crystal manufacturer for
appropriate values of external
components.
6.6 Resetting Timer1 Using a CCP
Trigger Output
If the CCP1 or CCP2 module is configured in Compare
mode to generate a “special event trigger”
(CCP1M3:CCP1M0 = 1011), this signal will reset
Timer1.
Note: The special event triggers from the CCP1
and CCP2 modules will not set interrupt
flag bit, TMR1IF (PIR1<0>).
Timer1 must be configured for either Timer or Synchro-nized
Counter mode to take advantage of this feature.
If Timer1 is running in Asynchronous Counter mode,
this Reset operation may not work.
In the event that a write to Timer1 coincides with a
special event trigger from CCP1 or CCP2, the write will
take precedence.
In this mode of operation, the CCPRxH:CCPRxL regis-ter
pair effectively becomes the period register for
Timer1.

PIC16F87XA
6.7 Resetting of Timer1 Register Pair
(TMR1H, TMR1L)
TMR1H and TMR1L registers are not reset to 00h on a
POR, or any other Reset, except by the CCP1 and
CCP2 special event triggers.
T1CON register is reset to 00h on a Power-on Reset,
or a Brown-out Reset, which shuts off the timer and
leaves a 1:1 prescale. In all other Resets, the register
is unaffected.
6.8 Timer1 Prescaler
The prescaler counter is cleared on writes to the
TMR1H or TMR1L registers.
TABLE 6-2: REGISTERS ASSOCIATED WITH TIMER1 AS A TIMER/COUNTER
Value on:
POR, BOR
Value on
all other
Resets
0Bh,8Bh,
10Bh, 18Bh
0Eh TMR1L Holding Register for the Least Significant Byte of the 16-bit TMR1 Register xxxx xxxx uuuu uuuu
0Fh TMR1H Holding Register for the Most Significant Byte of the 16-bit TMR1 Register xxxx xxxx uuuu uuuu
10h T1CON — — T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON --00 0000 --uu uuuu
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are not used by the Timer1 module.
Note 1: Bits PSPIE and PSPIF are reserved on the 28-pin devices; always maintain these bits clear.

PIC16F87XA
7.0 TIMER2 MODULE
Timer2 is an 8-bit timer with a prescaler and a
postscaler. It can be used as the PWM time base for the
PWM mode of the CCP module(s). The TMR2 register
is readable and writable and is cleared on any device
Reset.
The input clock (FOSC/4) has a prescale option of
1:1, 1:4 or 1:16, selected by control bits
T2CKPS1:T2CKPS0 (T2CON<1:0>).
The Timer2 module has an 8-bit period register, PR2.
Timer2 increments from 00h until it matches PR2 and
then resets to 00h on the next increment cycle. PR2 is
a readable and writable register. The PR2 register is
initialized to FFh upon Reset.
The match output of TMR2 goes through a 4-bit
postscaler (which gives a 1:1 to 1:16 scaling inclusive)
to generate a TMR2 interrupt (latched in flag bit,
TMR2IF (PIR1<1>)).
Timer2 can be shut-off by clearing control bit, TMR2ON
(T2CON<2>), to minimize power consumption.
Register 7-1 shows the Timer2 Control register.
Additional information on timer modules is available in
Manual (DS33023).
FIGURE 7-1: TIMER2 BLOCK DIAGRAM
TMR2 Reg
Comparator
TMR2
Sets Flag
Output(1)
Reset
bit TMR2IF
Postscaler
PR2 Reg
1:1 to 1:16
EQ
4
T2OUTPS3:
T2OUTPS0
T2CKPS1:
T2CKPS0
Note 1: TMR2 register output can be software selected by the
SSP module as a baud clock.
REGISTER 7-1: T2CON: TIMER2 CONTROL REGISTER (ADDRESS 12h)
Prescaler
1:1, 1:4, 1:16
2
FOSC/4
U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
— TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON T2CKPS1 T2CKPS0
bit 7 bit 0
bit 6-3 TOUTPS3:TOUTPS0: Timer2 Output Postscale Select bits
0000 = 1:1 postscale
•
•
•
bit 2 TMR2ON: Timer2 On bit
1 = Timer2 is on
0 = Timer2 is off
bit 1-0 T2CKPS1:T2CKPS0: Timer2 Clock Prescale Select bits
00 = Prescaler is 1
01 = Prescaler is 4
1x = Prescaler is 16
Legend:

PIC16F87XA
7.1 Timer2 Prescaler and Postscaler
The prescaler and postscaler counters are cleared
when any of the following occurs:
• a write to the TMR2 register
• a write to the T2CON register
• any device Reset (POR, MCLR Reset, WDT
Reset or BOR)
TMR2 is not cleared when T2CON is written.
7.2 Output of TMR2
The output of TMR2 (before the postscaler) is fed to the
SSP module, which optionally uses it to generate the
shift clock.
TABLE 7-1: REGISTERS ASSOCIATED WITH TIMER2 AS A TIMER/COUNTER
Value on:
POR, BOR
Value on
all other
Resets
0Bh, 8Bh,
10Bh, 18Bh
11h TMR2 Timer2 Module’s Register 0000 0000 0000 0000
12h T2CON — TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000 -000 0000
92h PR2 Timer2 Period Register 1111 1111 1111 1111
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are not used by the Timer2 module.
Note 1: Bits PSPIE and PSPIF are reserved on 28-pin devices; always maintain these bits clear.

PIC16F87XA
8.0 CAPTURE/COMPARE/PWM
MODULES
Each Capture/Compare/PWM (CCP) module contains
a 16-bit register which can operate as a:
• 16-bit Capture register
• 16-bit Compare register
• PWM Master/Slave Duty Cycle register
Both the CCP1 and CCP2 modules are identical in
operation, with the exception being the operation of the
special event trigger. Table 8-1 and Table 8-2 show the
resources and interactions of the CCP module(s). In
the following sections, the operation of a CCP module
is described with respect to CCP1. CCP2 operates the
same as CCP1 except where noted.
CCP1 Module:
Capture/Compare/PWM Register 1 (CCPR1) is com-prised
of two 8-bit registers: CCPR1L (low byte) and
CCPR1H (high byte). The CCP1CON register controls
the operation of CCP1. The special event trigger is
generated by a compare match and will reset Timer1.
CCP2 Module:
Capture/Compare/PWM Register 2 (CCPR2) is com-prised
of two 8-bit registers: CCPR2L (low byte) and
CCPR2H (high byte). The CCP2CON register controls
the operation of CCP2. The special event trigger is
generated by a compare match and will reset Timer1
and start an A/D conversion (if the A/D module is
enabled).
Additional information on CCP modules is available in
Manual (DS33023) and in application note AN594,
“Using the CCP Module(s)” (DS00594).
TABLE 8-1: CCP MODE – TIMER
RESOURCES REQUIRED
TABLE 8-2: INTERACTION OF TWO CCP MODULES
CCP Mode Timer Resource
Capture
Compare
PWM
Timer1
Timer1
Timer2
CCPx Mode CCPy Mode Interaction
Capture Capture Same TMR1 time base
Capture Compare The compare should be configured for the special event trigger which clears TMR1
Compare Compare The compare(s) should be configured for the special event trigger which clears TMR1
PWM PWM The PWMs will have the same frequency and update rate (TMR2 interrupt)
PWM Capture None
PWM Compare None

PIC16F87XA
REGISTER 8-1: CCP1CON REGISTER/CCP2CON REGISTER (ADDRESS 17h/1Dh)
U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
— — CCPxX CCPxY CCPxM3 CCPxM2 CCPxM1 CCPxM0
bit 7 bit 0
bit 5-4 CCPxX:CCPxY: PWM Least Significant bits
Capture mode:
Unused.
Compare mode:
Unused.
PWM mode:
These bits are the two LSbs of the PWM duty cycle. The eight MSbs are found in CCPRxL.
bit 3-0 CCPxM3:CCPxM0: CCPx Mode Select bits
0000 = Capture/Compare/PWM disabled (resets CCPx module)
0100 = Capture mode, every falling edge
0101 = Capture mode, every rising edge
0110 = Capture mode, every 4th rising edge
0111 = Capture mode, every 16th rising edge
1000 = Compare mode, set output on match (CCPxIF bit is set)
1001 = Compare mode, clear output on match (CCPxIF bit is set)
1010 = Compare mode, generate software interrupt on match (CCPxIF bit is set, CCPx pin is
unaffected)
1011 = Compare mode, trigger special event (CCPxIF bit is set, CCPx pin is unaffected); CCP1
resets TMR1; CCP2 resets TMR1 and starts an A/D conversion (if A/D module is
enabled)
11xx = PWM mode
Legend:

PIC16F87XA
8.1 Capture Mode
In Capture mode, CCPR1H:CCPR1L captures the
16-bit value of the TMR1 register when an event occurs
on pin RC2/CCP1. An event is defined as one of the
following:
• Every falling edge
• Every rising edge
• Every 4th rising edge
• Every 16th rising edge
The type of event is configured by control bits,
CCP1M3:CCP1M0 (CCPxCON<3:0>). When a cap-ture
is made, the interrupt request flag bit, CCP1IF
(PIR1<2>), is set. The interrupt flag must be cleared in
software. If another capture occurs before the value in
register CCPR1 is read, the old captured value is
overwritten by the new value.
8.1.1 CCP PIN CONFIGURATION
In Capture mode, the RC2/CCP1 pin should be
configured as an input by setting the TRISC<2> bit.
Note: If the RC2/CCP1 pin is configured as an
output, a write to the port can cause a
Capture condition.
FIGURE 8-1: CAPTURE MODE
OPERATION BLOCK
DIAGRAM
8.1.2 TIMER1 MODE SELECTION
Timer1 must be running in Timer mode, or Synchro-nized
Counter mode, for the CCP module to use the
capture feature. In Asynchronous Counter mode, the
capture operation may not work.
8.1.3 SOFTWARE INTERRUPT
When the Capture mode is changed, a false capture
interrupt may be generated. The user should keep bit
CCP1IE (PIE1<2>) clear to avoid false interrupts and
should clear the flag bit, CCP1IF, following any such
change in operating mode.
8.1.4 CCP PRESCALER
There are four prescaler settings, specified by bits
CCP1M3:CCP1M0. Whenever the CCP module is
turned off, or the CCP module is not in Capture mode,
the prescaler counter is cleared. Any Reset will clear
the prescaler counter.
Switching from one capture prescaler to another may
generate an interrupt. Also, the prescaler counter will
not be cleared, therefore, the first capture may be from
a non-zero prescaler. Example 8-1 shows the recom-mended
method for switching between capture
prescalers. This example also clears the prescaler
counter and will not generate the “false” interrupt.
EXAMPLE 8-1: CHANGING BETWEEN
CAPTURE PRESCALERS
Set Flag bit CCP1IF
CCPR1H CCPR1L
Capture
Enable
TMR1H TMR1L
(PIR1<2>)
Prescaler
÷ 1, 4, 16
Edge Detect
Qs
and
CCP1CON<3:0>
RC2/CCP1
pin
CLRF CCP1CON ; Turn CCP module off
MOVLW NEW_CAPT_PS ; Load the W reg with
; the new prescaler
; move value and CCP ON
MOVWF CCP1CON ; Load CCP1CON with this
; value

PIC16F87XA
8.2 Compare Mode
In Compare mode, the 16-bit CCPR1 register value is
constantly compared against the TMR1 register pair
value. When a match occurs, the RC2/CCP1 pin is:
• Driven high
• Driven low
• Remains unchanged
The action on the pin is based on the value of control
bits, CCP1M3:CCP1M0 (CCP1CON<3:0>). At the
same time, interrupt flag bit CCP1IF is set.
FIGURE 8-2: COMPARE MODE
OPERATION BLOCK
DIAGRAM
reset Timer1, but not set interrupt flag bit TMR1IF (PIR1<0>)
and set bit GO/DONE (ADCON0<2>).
Set Flag bit CCP1IF
(PIR1<2>)
CCPR1H CCPR1L
Comparator
TMR1H TMR1L
Special event trigger will:
Special Event Trigger
Q S
R
Output
Logic
Match
RC2/CCP1
pin
TRISC<2>
CCP1CON<3:0>
Mode Select
Output Enable
8.2.1 CCP PIN CONFIGURATION
The user must configure the RC2/CCP1 pin as an
output by clearing the TRISC<2> bit.
8.2.2 TIMER1 MODE SELECTION
Timer1 must be running in Timer mode, or Synchro-nized
Counter mode, if the CCP module is using the
compare feature. In Asynchronous Counter mode, the
compare operation may not work.
8.2.3 SOFTWARE INTERRUPT MODE
When Generate Software Interrupt mode is chosen, the
CCP1 pin is not affected. The CCPIF bit is set, causing
a CCP interrupt (if enabled).
8.2.4 SPECIAL EVENT TRIGGER
In this mode, an internal hardware trigger is generated
which may be used to initiate an action.
The special event trigger output of CCP1 resets the
TMR1 register pair. This allows the CCPR1 register to
effectively be a 16-bit programmable period register for
Timer1.
The special event trigger output of CCP2 resets the
TMR1 register pair and starts an A/D conversion (if the
A/D module is enabled).
Note: Clearing the CCP1CON register will force
the RC2/CCP1 compare output latch to
the default low level. This is not the
PORTC I/O data latch.
Note: The special event trigger from the CCP1
and CCP2 modules will not set interrupt
flag bit TMR1IF (PIR1<0>).

PIC16F87XA
8.3 PWM Mode (PWM)
In Pulse Width Modulation mode, the CCPx pin
produces up to a 10-bit resolution PWM output. Since
the CCP1 pin is multiplexed with the PORTC data latch,
the TRISC<2> bit must be cleared to make the CCP1
pin an output.
Note: Clearing the CCP1CON register will force
the CCP1 PWM output latch to the default
low level. This is not the PORTC I/O data
latch.
Figure 8-3 shows a simplified block diagram of the
CCP module in PWM mode.
For a step-by-step procedure on how to set up the CCP
module for PWM operation, see Section 8.3.3 “Setup
for PWM Operation”.
FIGURE 8-3: SIMPLIFIED PWM BLOCK
DIAGRAM
Duty Cycle Registers CCP1CON<5:4>
CCPR1L
CCPR1H (Slave)
Comparator
TMR2
Comparator
PR2
(Note 1)
R Q
S
Clear Timer,
CCP1 pin and
latch D.C.
RC2/CCP1
TRISC<2>
Note 1: The 8-bit timer is concatenated with 2-bit internal Q
clock, or 2 bits of the prescaler, to create 10-bit time
base.
A PWM output (Figure 8-4) has a time base (period)
and a time that the output stays high (duty cycle). The
frequency of the PWM is the inverse of the period
(1/period).
FIGURE 8-4: PWM OUTPUT
8.3.1 PWM PERIOD
The PWM period is specified by writing to the PR2
register. The PWM period can be calculated using the
following formula:
PWM Period = [(PR2) + 1] • 4 • TOSC •
(TMR2 Prescale Value)
PWM frequency is defined as 1/[PWM period].
When TMR2 is equal to PR2, the following three events
occur on the next increment cycle:
• TMR2 is cleared
• The CCP1 pin is set (exception: if PWM duty
cycle = 0%, the CCP1 pin will not be set)
• The PWM duty cycle is latched from CCPR1L into
CCPR1H
Note: The Timer2 postscaler (see Section 7.1
“Timer2 Prescaler and Postscaler”) is
not used in the determination of the PWM
frequency. The postscaler could be used
to have a servo update rate at a different
frequency than the PWM output.
8.3.2 PWM DUTY CYCLE
The PWM duty cycle is specified by writing to the
CCPR1L register and to the CCP1CON<5:4> bits. Up
to 10-bit resolution is available. The CCPR1L contains
the eight MSbs and the CCP1CON<5:4> contains the
two LSbs. This 10-bit value is represented by
CCPR1L:CCP1CON<5:4>. The following equation is
used to calculate the PWM duty cycle in time:
PWM Duty Cycle =(CCPR1L:CCP1CON<5:4>) •
TOSC • (TMR2 Prescale Value)
CCPR1L and CCP1CON<5:4> can be written to at any
time, but the duty cycle value is not latched into
CCPR1H until after a match between PR2 and TMR2
occurs (i.e., the period is complete). In PWM mode,
CCPR1H is a read-only register.
The CCPR1H register and a 2-bit internal latch are
used to double-buffer the PWM duty cycle. This
double-buffering is essential for glitch-free PWM
operation.
When the CCPR1H and 2-bit latch match TMR2,
concatenated with an internal 2-bit Q clock or 2 bits of
the TMR2 prescaler, the CCP1 pin is cleared.
The maximum PWM resolution (bits) for a given PWM
frequency is given by the following formula.
EQUATION 8-1:
Period
Duty Cycle
TMR2 = PR2
TMR2 = PR2
TMR2 = Duty Cycle
FOSC )
log(FPWM
Resolution = bits
log(2)
Note: If the PWM duty cycle value is longer than
the PWM period, the CCP1 pin will not be
cleared.

PIC16F87XA
8.3.3 SETUP FOR PWM OPERATION
The following steps should be taken when configuring
the CCP module for PWM operation:
1. Set the PWM period by writing to the PR2 register.
2. Set the PWM duty cycle by writing to the
CCPR1L register and CCP1CON<5:4> bits.
3. Make the CCP1 pin an output by clearing the
TRISC<2> bit.
4. Set the TMR2 prescale value and enable Timer2
by writing to T2CON.
5. Configure the CCP1 module for PWM operation.
TABLE 8-3: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 20 MHz
PWM Frequency 1.22 kHz 4.88 kHz 19.53 kHz 78.12kHz 156.3 kHz 208.3 kHz
Timer Prescaler (1, 4, 16) 16 4 1 1 1 1
PR2 Value 0xFFh 0xFFh 0xFFh 0x3Fh 0x1Fh 0x17h
Maximum Resolution (bits) 10 10 10 8 7 5.5
TABLE 8-4: REGISTERS ASSOCIATED WITH CAPTURE, COMPARE AND TIMER1
Value on:
POR, BOR
Value on
all other
Resets
0Bh,8Bh,
10Bh, 18Bh
0Dh PIR2 — — — — — — — CCP2IF ---- ---0 ---- ---0
8Dh PIE2 — — — — — — — CCP2IE ---- ---0 ---- ---0
0Eh TMR1L Holding Register for the Least Significant Byte of the 16-bit TMR1 Register xxxx xxxx uuuu uuuu
0Fh TMR1H Holding Register for the Most Significant Byte of the 16-bit TMR1 Register xxxx xxxx uuuu uuuu
10h T1CON — — T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON --00 0000 --uu uuuu
15h CCPR1L Capture/Compare/PWM Register 1 (LSB) xxxx xxxx uuuu uuuu
16h CCPR1H Capture/Compare/PWM Register 1 (MSB) xxxx xxxx uuuu uuuu
17h CCP1CON — — CCP1X CCP1Y CCP1M3 CCP1M2 CCP1M1 CCP1M0 --00 0000 --00 0000
1Bh CCPR2L Capture/Compare/PWM Register 2 (LSB) xxxx xxxx uuuu uuuu
1Ch CCPR2H Capture/Compare/PWM Register 2 (MSB) xxxx xxxx uuuu uuuu
1Dh CCP2CON — — CCP2X CCP2Y CCP2M3 CCP2M2 CCP2M1 CCP2M0 --00 0000 --00 0000
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are not used by Capture and Timer1.
Note 1: The PSP is not implemented on 28-pin devices; always maintain these bits clear.

PIC16F87XA
TABLE 8-5: REGISTERS ASSOCIATED WITH PWM AND TIMER2
Value on:
POR, BOR
Value on
all other
Resets
0Bh,8Bh,
10Bh, 18Bh
0Dh PIR2 — — — — — — — CCP2IF ---- ---0 ---- ---0
8Dh PIE2 — — — — — — — CCP2IE ---- ---0 ---- ---0
11h TMR2 Timer2 Module’s Register 0000 0000 0000 0000
92h PR2 Timer2 Module’s Period Register 1111 1111 1111 1111
12h T2CON — TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000 -000 0000
15h CCPR1L Capture/Compare/PWM Register 1 (LSB) xxxx xxxx uuuu uuuu
16h CCPR1H Capture/Compare/PWM Register 1 (MSB) xxxx xxxx uuuu uuuu
17h CCP1CON — — CCP1X CCP1Y CCP1M3 CCP1M2 CCP1M1 CCP1M0 --00 0000 --00 0000
1Bh CCPR2L Capture/Compare/PWM Register 2 (LSB) xxxx xxxx uuuu uuuu
1Ch CCPR2H Capture/Compare/PWM Register 2 (MSB) xxxx xxxx uuuu uuuu
1Dh CCP2CON — — CCP2X CCP2Y CCP2M3 CCP2M2 CCP2M1 CCP2M0 --00 0000 --00 0000
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are not used by PWM and Timer2.

PIC16F87XA
NOTES:

PIC16F87XA
9.0 MASTER SYNCHRONOUS
SERIAL PORT (MSSP)
MODULE
9.1 Master SSP (MSSP) Module
Overview
The Master Synchronous Serial Port (MSSP) module is
a serial interface, useful for communicating with other
peripheral or microcontroller devices. These peripheral
devices may be serial EEPROMs, shift registers,
display drivers, A/D converters, etc. The MSSP module
can operate in one of two modes:
• Serial Peripheral Interface (SPI)
• Inter-Integrated Circuit (I2C)
- Full Master mode
- Slave mode (with general address call)
The I2C interface supports the following modes in
hardware:
• Master mode
• Multi-Master mode
• Slave mode
9.2 Control Registers
The MSSP module has three associated registers.
These include a status register (SSPSTAT) and two
control registers (SSPCON and SSPCON2). The use
of these registers and their individual configuration bits
differ significantly, depending on whether the MSSP
module is operated in SPI or I2C mode.
Additional details are provided under the individual
sections.
9.3 SPI Mode
The SPI mode allows 8 bits of data to be synchronously
transmitted and received simultaneously. All four
modes of SPI are supported. To accomplish
communication, typically three pins are used:
• Serial Data Out (SDO) – RC5/SDO
• Serial Data In (SDI) – RC4/SDI/SDA
• Serial Clock (SCK) – RC3/SCK/SCL
Additionally, a fourth pin may be used when in a Slave
mode of operation:
• Slave Select (SS) – RA5/AN4/SS/C2OUT
Figure 9-1 shows the block diagram of the MSSP
module when operating in SPI mode.
FIGURE 9-1: MSSP BLOCK DIAGRAM
(SPI MODE)
Internal
Data Bus
Read Write
SSPBUF reg
SSPSR reg
bit0 Shift
Peripheral OE
SS Control
Enable
2
Clock Select
SSPM3:SSPM0
Clock
Edge
Select
( TMR2 Output
)
2
Prescaler TOSC
4, 16, 64
SMP:CKE
2
Edge
Select
4
Data to TX/RX in SSPSR
TRIS bit
RC4/SDI/SDA
RC5/SDO
RA5/AN4/
SS/C2OUT
RC3/SCK/SCL
Note: When the SPI is in Slave mode with SS pin
control enabled (SSPCON<3:0> = 0100),
the state of the SS pin can affect the state
read back from the TRISC<5> bit. The
Peripheral OE signal from the SSP mod-ule
in PORTC controls the state that is
read back from the TRISC<5> bit (see
Section 4.3 “PORTC and the TRISC
Register” for information on PORTC). If
Read-Modify-Write instructions, such as
BSF, are performed on the TRISC register
while the SS pin is high, this will cause the
TRISC<5> bit to be set, thus disabling the
SDO output.

PIC16F87XA
9.3.1 REGISTERS
The MSSP module has four registers for SPI mode
operation. These are:
• MSSP Control Register (SSPCON)
• MSSP Status Register (SSPSTAT)
• Serial Receive/Transmit Buffer Register
(SSPBUF)
• MSSP Shift Register (SSPSR) – Not directly
accessible
SSPCON and SSPSTAT are the control and status
registers in SPI mode operation. The SSPCON regis-ter
is readable and writable. The lower six bits of the
SSPSTAT are read-only. The upper two bits of the
SSPSTAT are read/write.
SSPSR is the shift register used for shifting data in or
out. SSPBUF is the buffer register to which data bytes
are written to or read from.
In receive operations, SSPSR and SSPBUF together
create a double-buffered receiver. When SSPSR
receives a complete byte, it is transferred to SSPBUF
and the SSPIF interrupt is set.
During transmission, the SSPBUF is not double-buffered.
A write to SSPBUF will write to both SSPBUF
and SSPSR.
REGISTER 9-1: SSPSTAT: MSSP STATUS REGISTER (SPI MODE) (ADDRESS 94h)
R/W-0 R/W-0 R-0 R-0 R-0 R-0 R-0 R-0
SMP CKE D/A P S R/W UA BF
bit 7 bit 0
bit 7 SMP: Sample bit
SPI Master mode:
1 = Input data sampled at end of data output time
0 = Input data sampled at middle of data output time
SPI Slave mode:
SMP must be cleared when SPI is used in Slave mode.
bit 6 CKE: SPI Clock Select bit
1 = Transmit occurs on transition from active to Idle clock state
0 = Transmit occurs on transition from Idle to active clock state
Note: Polarity of clock state is set by the CKP bit (SSPCON1<4>).
bit 5 D/A: Data/Address bit
Used in I2C mode only.
bit 4 P: Stop bit
Used in I2C mode only. This bit is cleared when the MSSP module is disabled, SSPEN is cleared.
bit 3 S: Start bit
bit 2 R/W: Read/Write bit information
bit 1 UA: Update Address bit
bit 0 BF: Buffer Full Status bit (Receive mode only)
1 = Receive complete, SSPBUF is full
0 = Receive not complete, SSPBUF is empty
Legend:

PIC16F87XA
REGISTER 9-2: SSPCON1: MSSP CONTROL REGISTER 1 (SPI MODE) (ADDRESS 14h)
WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0
bit 7 bit 0
bit 7 WCOL: Write Collision Detect bit (Transmit mode only)
1 = The SSPBUF register is written while it is still transmitting the previous word. (Must be
cleared in software.)
0 = No collision
bit 6 SSPOV: Receive Overflow Indicator bit
SPI Slave mode:
1 = A new byte is received while the SSPBUF register is still holding the previous data. In case
of overflow, the data in SSPSR is lost. Overflow can only occur in Slave mode. The user
must read the SSPBUF, even if only transmitting data, to avoid setting overflow. (Must be
0 = No overflow
Note: In Master mode, the overflow bit is not set, since each new reception (and
transmission) is initiated by writing to the SSPBUF register.
bit 5 SSPEN: Synchronous Serial Port Enable bit
1 = Enables serial port and configures SCK, SDO, SDI, and SS as serial port pins
0 = Disables serial port and configures these pins as I/O port pins
Note: When enabled, these pins must be properly configured as input or output.
bit 4 CKP: Clock Polarity Select bit
1 = Idle state for clock is a high level
0 = Idle state for clock is a low level
bit 3-0 SSPM3:SSPM0: Synchronous Serial Port Mode Select bits
0101 = SPI Slave mode, clock = SCK pin. SS pin control disabled. SS can be used as I/O pin.
0100 = SPI Slave mode, clock = SCK pin. SS pin control enabled.
0011 = SPI Master mode, clock = TMR2 output/2
0010 = SPI Master mode, clock = FOSC/64
Note: Bit combinations not specifically listed here are either reserved or implemented in
I2C mode only.
Legend:

PIC16F87XA
9.3.2 OPERATION
When initializing the SPI, several options need to be
specified. This is done by programming the appropriate
control bits (SSPCON<5:0> and SSPSTAT<7:6>).
These control bits allow the following to be specified:
• Master mode (SCK is the clock output)
• Slave mode (SCK is the clock input)
• Clock Polarity (Idle state of SCK)
• Data Input Sample Phase (middle or end of data
output time)
• Clock Edge (output data on rising/falling edge of
SCK)
• Clock Rate (Master mode only)
• Slave Select mode (Slave mode only)
The MSSP consists of a transmit/receive shift register
(SSPSR) and a buffer register (SSPBUF). The SSPSR
shifts the data in and out of the device, MSb first. The
SSPBUF holds the data that was written to the SSPSR
until the received data is ready. Once the eight bits of
data have been received, that byte is moved to the
SSPBUF register. Then, the Buffer Full detect bit, BF
(SSPSTAT<0>), and the interrupt flag bit, SSPIF, are
set. This double-buffering of the received data
(SSPBUF) allows the next byte to start reception before
reading the data that was just received. Any write to the
SSPBUF register during transmission/reception of data
will be ignored and the write collision detect bit, WCOL
(SSPCON<7>), will be set. User software must clear
the WCOL bit so that it can be determined if the follow-ing
write(s) to the SSPBUF register completed
successfully.
When the application software is expecting to receive
valid data, the SSPBUF should be read before the next
byte of data to transfer is written to the SSPBUF. Buffer
Full bit, BF (SSPSTAT<0>), indicates when SSPBUF
has been loaded with the received data (transmission
is complete). When the SSPBUF is read, the BF bit is
cleared. This data may be irrelevant if the SPI is only a
transmitter. Generally, the MSSP interrupt is used to
determine when the transmission/reception has com-pleted.
The SSPBUF must be read and/or written. If the
interrupt method is not going to be used, then software
polling can be done to ensure that a write collision does
not occur. Example 9-1 shows the loading of the
SSPBUF (SSPSR) for data transmission.
The SSPSR is not directly readable or writable and can
only be accessed by addressing the SSPBUF register.
Additionally, the MSSP Status register (SSPSTAT)
indicates the various status conditions.
EXAMPLE 9-1: LOADING THE SSPBUF (SSPSR) REGISTER
LOOP BTFSS SSPSTAT, BF ;Has data been received(transmit complete)?
BRA LOOP ;No
MOVF SSPBUF, W ;WREG reg = contents of SSPBUF
MOVWF RXDATA ;Save in user RAM, if data is meaningful
MOVF TXDATA, W ;W reg = contents of TXDATA
MOVWF SSPBUF ;New data to xmit

PIC16F87XA
9.3.3 ENABLING SPI I/O
To enable the serial port, SSP Enable bit, SSPEN
(SSPCON<5>), must be set. To reset or reconfigure
SPI mode, clear the SSPEN bit, re-initialize the
SSPCON registers and then set the SSPEN bit. This
configures the SDI, SDO, SCK and SS pins as serial
port pins. For the pins to behave as the serial port func-tion,
some must have their data direction bits (in the
TRIS register) appropriately programmed. That is:
• SDI is automatically controlled by the SPI module
• SDO must have TRISC<5> bit cleared
• SCK (Master mode) must have TRISC<3> bit
cleared
• SCK (Slave mode) must have TRISC<3> bit set
• SS must have TRISC<4> bit set
Any serial port function that is not desired may be
overridden by programming the corresponding data
direction (TRIS) register to the opposite value.
9.3.4 TYPICAL CONNECTION
Figure 9-2 shows a typical connection between two
microcontrollers. The master controller (Processor 1)
initiates the data transfer by sending the SCK signal.
Data is shifted out of both shift registers on their
programmed clock edge and latched on the opposite
edge of the clock. Both processors should be
programmed to the same Clock Polarity (CKP), then
both controllers would send and receive data at the
same time. Whether the data is meaningful (or dummy
data) depends on the application software. This leads
to three scenarios for data transmission:
• Master sends data – Slave sends dummy data
• Master sends data – Slave sends data
• Master sends dummy data – Slave sends data
FIGURE 9-2: SPI MASTER/SLAVE CONNECTION
SPI Master SSPM3:SSPM0 = 00xxb
Serial Input Buffer
(SSPBUF)
Shift Register
(SSPSR)
MSb LSb
SDO
SDI
PROCESSOR 1
SCK
SPI Slave SSPM3:SSPM0 = 010xb
Serial Input Buffer
(SSPBUF)
Shift Register
(SSPSR)
MSb LSb
SDI
SDO
PROCESSOR 2
SCK
Serial Clock

PIC16F87XA
9.3.5 MASTER MODE
The master can initiate the data transfer at any time
because it controls the SCK. The master determines
when the slave (Processor 2, Figure 9-2) is to
broadcast data by the software protocol.
In Master mode, the data is transmitted/received as
soon as the SSPBUF register is written to. If the SPI is
only going to receive, the SDO output could be
disabled (programmed as an input). The SSPSR
register will continue to shift in the signal present on the
SDI pin at the programmed clock rate. As each byte is
received, it will be loaded into the SSPBUF register as
if a normal received byte (interrupts and status bits
appropriately set). This could be useful in receiver
applications as a “Line Activity Monitor” mode.
The clock polarity is selected by appropriately program-ming
the CKP bit (SSPCON<4>). This then, would give
waveforms for SPI communication as shown in
Figure 9-3, Figure 9-5 and Figure 9-6, where the MSB
is transmitted first. In Master mode, the SPI clock rate
(bit rate) is user programmable to be one of the
following:
• FOSC/4 (or TCY)
• FOSC/16 (or 4 • TCY)
• FOSC/64 (or 16 • TCY)
• Timer2 output/2
This allows a maximum data rate (at 40 MHz) of
10.00 Mbps.
Figure 9-3 shows the waveforms for Master mode.
When the CKE bit is set, the SDO data is valid before
there is a clock edge on SCK. The change of the input
sample is shown based on the state of the SMP bit. The
time when the SSPBUF is loaded with the received
data is shown.
FIGURE 9-3: SPI MODE WAVEFORM (MASTER MODE)
Write to
SSPBUF
SCK
(CKP = 0
CKE = 0)
SCK
(CKP = 1
CKE = 0)
SCK
(CKP = 0
CKE = 1)
SCK
(CKP = 1
4 Clock
Modes
CKE = 1)
SDO
(CKE = 0)
SDO
(CKE = 1)
SDI
(SMP = 0)
Input
Sample
(SMP = 0)
SDI
(SMP = 1)
Input
Sample
bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
bit 7 bit 0
bit 7 bit 0
(SMP = 1)
SSPIF
SSPSR to
SSPBUF
Next Q4 Cycle
after Q2↓

PIC16F87XA
9.3.6 SLAVE MODE
In Slave mode, the data is transmitted and received as
the external clock pulses appear on SCK. When the
last bit is latched, the SSPIF interrupt flag bit is set.
While in Slave mode, the external clock is supplied by
the external clock source on the SCK pin. This external
clock must meet the minimum high and low times as
specified in the electrical specifications.
While in Sleep mode, the slave can transmit/receive
data. When a byte is received, the device will wake-up
from Sleep.
9.3.7 SLAVE SELECT
SYNCHRONIZATION
The SS pin allows a Synchronous Slave mode. The
SPI must be in Slave mode with SS pin control enabled
(SSPCON<3:0> = 04h). The pin must not be driven low
for the SS pin to function as an input. The data latch
must be high. When the SS pin is low, transmission and
reception are enabled and the SDO pin is driven. When
the SS pin goes high, the SDO pin is no longer driven
even if in the middle of a transmitted byte and becomes
a floating output. External pull-up/pull-down resistors
may be desirable, depending on the application.
Note 1: When the SPI is in Slave mode with SS pin
control enabled (SSPCON<3:0> = 0100),
the SPI module will reset if the SS pin is set
to VDD.
2: If the SPI is used in Slave Mode with CKE
set, then the SS pin control must be
enabled.
When the SPI module resets, the bit counter is forced
to ‘0’. This can be done by either forcing the SS pin to
a high level or clearing the SSPEN bit.
To emulate two-wire communication, the SDO pin can
be connected to the SDI pin. When the SPI needs to
operate as a receiver, the SDO pin can be configured
as an input. This disables transmissions from the SDO.
The SDI can always be left as an input (SDI function)
since it cannot create a bus conflict.
FIGURE 9-4: SLAVE SYNCHRONIZATION WAVEFORM
SS
SCK
(CKP = 0
CKE = 0)
SCK
(CKP = 1
CKE = 0)
Write to
SSPBUF
SDO bit 7 bit 6 bit 7
SDI
(SMP = 0)
Input
Sample
bit 7
(SMP = 0)
SSPIF
Interrupt
Flag
SSPSR to
SSPBUF
bit 0
bit 7
bit 0
Next Q4 Cycle
after Q2↓

PIC16F87XA
FIGURE 9-5: SPI MODE WAVEFORM (SLAVE MODE WITH CKE = 0)
SS
Optional
SCK
(CKP = 0
CKE = 0)
SCK
(CKP = 1
CKE = 0)
Write to
SSPBUF
SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
SDI
(SMP = 0)
Input
Sample
bit 7 bit 0
(SMP = 0)
SSPIF
Interrupt
Flag
SSPSR to
SSPBUF
FIGURE 9-6: SPI MODE WAVEFORM (SLAVE MODE WITH CKE = 1)
Next Q4 Cycle
after Q2↓
SS
Not Optional
SCK
(CKP = 0
CKE = 1)
SCK
(CKP = 1
CKE = 1)
Write to
SSPBUF
SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
SDI
(SMP = 0)
Input
Sample
bit 7 bit 0
(SMP = 0)
SSPIF
Interrupt
Flag
SSPSR to
SSPBUF
Next Q4 Cycle
after Q2↓

PIC16F87XA
9.3.8 SLEEP OPERATION
In Master mode, all module clocks are halted and the
transmission/reception will remain in that state until the
device wakes from Sleep. After the device returns to
normal mode, the module will continue to transmit/
receive data.
In Slave mode, the SPI Transmit/Receive Shift register
operates asynchronously to the device. This allows the
device to be placed in Sleep mode and data to be
shifted into the SPI Transmit/Receive Shift register.
When all 8 bits have been received, the MSSP interrupt
flag bit will be set and if enabled, will wake the device
from Sleep.
9.3.9 EFFECTS OF A RESET
A Reset disables the MSSP module and terminates the
current transfer.
9.3.10 BUS MODE COMPATIBILITY
Table 9-1 shows the compatibility between the
standard SPI modes and the states of the CKP and
CKE control bits.
TABLE 9-1: SPI BUS MODES
Standard SPI Mode
Terminology
Control Bits State
CKP CKE
0, 0 0 1
0, 1 0 0
1, 0 1 1
1, 1 1 0
There is also a SMP bit which controls when the data is
sampled.
TABLE 9-2: REGISTERS ASSOCIATED WITH SPI OPERATION
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Value on
POR, BOR
Value on
all other
Resets
INTCON GIE/
GIEH
PEIE/
GIEL
TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 0000 000x 0000 000u
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 0000 0000
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 0000 0000 0000 0000
TRISC PORTC Data Direction Register 1111 1111 1111 1111
SSPBUF Synchronous Serial Port Receive Buffer/Transmit Register xxxx xxxx uuuu uuuu
SSPCON WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 0000 0000
TRISA — PORTA Data Direction Register --11 1111 --11 1111
SSPSTAT SMP CKE D/A P S R/W UA BF 0000 0000 0000 0000
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’.
Shaded cells are not used by the MSSP in SPI mode.
Note 1: The PSPIF, PSPIE and PSPIP bits are reserved on 28-pin devices; always maintain these bits clear.

PIC16F87XA
9.4 I2C Mode
The MSSP module in I2C mode fully implements all
master and slave functions (including general call sup-port)
and provides interrupts on Start and Stop bits in
hardware to determine a free bus (multi-master func-tion).
The MSSP module implements the standard
mode specifications, as well as 7-bit and 10-bit
addressing.
Two pins are used for data transfer:
• Serial clock (SCL) – RC3/SCK/SCL
• Serial data (SDA) – RC4/SDI/SDA
The user must configure these pins as inputs or outputs
through the TRISC<4:3> bits.
FIGURE 9-7: MSSP BLOCK DIAGRAM
(I2C MODE)
9.4.1 REGISTERS
The MSSP module has six registers for I2C operation.
These are:
• MSSP Control Register (SSPCON)
• MSSP Control Register 2 (SSPCON2)
• MSSP Status Register (SSPSTAT)
• Serial Receive/Transmit Buffer Register
(SSPBUF)
• MSSP Shift Register (SSPSR) – Not directly
accessible
• MSSP Address Register (SSPADD)
SSPCON, SSPCON2 and SSPSTAT are the control
and status registers in I2C mode operation. The
SSPCON and SSPCON2 registers are readable and
writable. The lower six bits of the SSPSTAT are
read-only. The upper two bits of the SSPSTAT are
read/write.
SSPSR is the shift register used for shifting data in or
out. SSPBUF is the buffer register to which data bytes
are written to or read from.
SSPADD register holds the slave device address
when the SSP is configured in I2C Slave mode. When
the SSP is configured in Master mode, the lower
seven bits of SSPADD act as the baud rate generator
reload value.
In receive operations, SSPSR and SSPBUF together
create a double-buffered receiver. When SSPSR
receives a complete byte, it is transferred to SSPBUF
and the SSPIF interrupt is set.
During transmission, the SSPBUF is not double-buffered.
A write to SSPBUF will write to both SSPBUF
and SSPSR.
Internal
Data Bus
Read Write
SSPBUF reg
SSPSR reg
MSb LSb
Match Detect
SSPADD reg
Start and
Stop bit Detect
Addr Match
Set, Reset
S, P bits
(SSPSTAT reg)
RC3/SCK/SCL
RC4/SDI/
Shift
Clock
SDA

PIC16F87XA
REGISTER 9-3: SSPSTAT: MSSP STATUS REGISTER (I2C MODE) (ADDRESS 94h)
R/W-0 R/W-0 R-0 R-0 R-0 R-0 R-0 R-0
SMP CKE D/A P S R/W UA BF
bit 7 bit 0
bit 7 SMP: Slew Rate Control bit
In Master or Slave mode:
1 = Slew rate control disabled for standard speed mode (100 kHz and 1 MHz)
0 = Slew rate control enabled for high-speed mode (400 kHz)
bit 6 CKE: SMBus Select bit
In Master or Slave mode:
1 = Enable SMBus specific inputs
0 = Disable SMBus specific inputs
bit 5 D/A: Data/Address bit
In Master mode:
Reserved.
In Slave mode:
1 = Indicates that the last byte received or transmitted was data
0 = Indicates that the last byte received or transmitted was address
bit 4 P: Stop bit
1 = Indicates that a Stop bit has been detected last
0 = Stop bit was not detected last
Note: This bit is cleared on Reset and when SSPEN is cleared.
bit 3 S: Start bit
1 = Indicates that a Start bit has been detected last
0 = Start bit was not detected last
Note: This bit is cleared on Reset and when SSPEN is cleared.
bit 2 R/W: Read/Write bit information (I2C mode only)
In Slave mode:
1 = Read
0 = Write
Note: This bit holds the R/W bit information following the last address match. This bit is
only valid from the address match to the next Start bit, Stop bit or not ACK bit.
In Master mode:
1 = Transmit is in progress
0 = Transmit is not in progress
Note: ORing this bit with SEN, RSEN, PEN, RCEN or ACKEN will indicate if the MSSP is
in Idle mode.
bit 1 UA: Update Address (10-bit Slave mode only)
1 = Indicates that the user needs to update the address in the SSPADD register
0 = Address does not need to be updated
bit 0 BF: Buffer Full Status bit
In Transmit mode:
1 = Receive complete, SSPBUF is full
0 = Receive not complete, SSPBUF is empty
In Receive mode:
1 = Data Transmit in progress (does not include the ACK and Stop bits), SSPBUF is full
0 = Data Transmit complete (does not include the ACK and Stop bits), SSPBUF is empty
Legend:

PIC16F87XA
REGISTER 9-4: SSPCON1: MSSP CONTROL REGISTER 1 (I2C MODE) (ADDRESS 14h)
WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0
bit 7 bit 0
bit 7 WCOL: Write Collision Detect bit
In Master Transmit mode:
1 = A write to the SSPBUF register was attempted while the I2C conditions were not valid for
a transmission to be started. (Must be cleared in software.)
0 = No collision
In Slave Transmit mode:
1 = The SSPBUF register is written while it is still transmitting the previous word. (Must be
0 = No collision
In Receive mode (Master or Slave modes):
This is a “don’t care” bit.
bit 6 SSPOV: Receive Overflow Indicator bit
In Receive mode:
1 = A byte is received while the SSPBUF register is still holding the previous byte. (Must be
0 = No overflow
In Transmit mode:
This is a “don’t care” bit in Transmit mode.
bit 5 SSPEN: Synchronous Serial Port Enable bit
1 = Enables the serial port and configures the SDA and SCL pins as the serial port pins
0 = Disables the serial port and configures these pins as I/O port pins
Note: When enabled, the SDA and SCL pins must be properly configured as input or output.
bit 4 CKP: SCK Release Control bit
In Slave mode:
1 = Release clock
0 = Holds clock low (clock stretch). (Used to ensure data setup time.)
In Master mode:
bit 3-0 SSPM3:SSPM0: Synchronous Serial Port Mode Select bits
1111 = I2C Slave mode, 10-bit address with Start and Stop bit interrupts enabled
1110 = I2C Slave mode, 7-bit address with Start and Stop bit interrupts enabled
1011 = I2C Firmware Controlled Master mode (Slave Idle)
1000 = I2C Master mode, clock = FOSC/(4 * (SSPADD + 1))
0111 = I2C Slave mode, 10-bit address
0110 = I2C Slave mode, 7-bit address
Note: Bit combinations not specifically listed here are either reserved or implemented in
SPI mode only.
Legend:

PIC16F87XA
REGISTER 9-5: SSPCON2: MSSP CONTROL REGISTER 2 (I2C MODE) (ADDRESS 91h)
GCEN ACKSTAT ACKDT ACKEN RCEN PEN RSEN SEN
bit 7 bit 0
bit 7 GCEN: General Call Enable bit (Slave mode only)
1 = Enable interrupt when a general call address (0000h) is received in the SSPSR
0 = General call address disabled
bit 6 ACKSTAT: Acknowledge Status bit (Master Transmit mode only)
1 = Acknowledge was not received from slave
0 = Acknowledge was received from slave
bit 5 ACKDT: Acknowledge Data bit (Master Receive mode only)
1 = Not Acknowledge
0 = Acknowledge
Note: Value that will be transmitted when the user initiates an Acknowledge sequence at
the end of a receive.
bit 4 ACKEN: Acknowledge Sequence Enable bit (Master Receive mode only)
1 = Initiate Acknowledge sequence on SDA and SCL pins and transmit ACKDT data bit.
Automatically cleared by hardware.
0 = Acknowledge sequence Idle
bit 3 RCEN: Receive Enable bit (Master mode only)
1 = Enables Receive mode for I2C
0 = Receive Idle
bit 2 PEN: Stop Condition Enable bit (Master mode only)
1 = Initiate Stop condition on SDA and SCL pins. Automatically cleared by hardware.
0 = Stop condition Idle
bit 1 RSEN: Repeated Start Condition Enabled bit (Master mode only)
1 = Initiate Repeated Start condition on SDA and SCL pins. Automatically cleared by hardware.
0 = Repeated Start condition Idle
bit 0 SEN: Start Condition Enabled/Stretch Enabled bit
In Master mode:
1 = Initiate Start condition on SDA and SCL pins. Automatically cleared by hardware.
0 = Start condition Idle
In Slave mode:
1 = Clock stretching is enabled for both slave transmit and slave receive (stretch enabled)
0 = Clock stretching is enabled for slave transmit only (PIC16F87X compatibility)
Legend:
Note: For bits ACKEN, RCEN, PEN, RSEN, SEN: If the I2C module is not in the Idle mode,
this bit may not be set (no spooling) and the SSPBUF may not be written (or writes
to the SSPBUF are disabled).

PIC16F87XA
9.4.2 OPERATION
The MSSP module functions are enabled by setting
MSSP Enable bit, SSPEN (SSPCON<5>).
The SSPCON register allows control of the I2C opera-tion.
Four mode selection bits (SSPCON<3:0>) allow
one of the following I2C modes to be selected:
• I2C Master mode, clock = OSC/4 (SSPADD + 1)
• I2C Slave mode (7-bit address)
• I2C Slave mode (10-bit address)
• I2C Slave mode (7-bit address) with Start and
Stop bit interrupts enabled
• I2C Slave mode (10-bit address) with Start and
Stop bit interrupts enabled
• I2C Firmware Controlled Master mode, slave is
Idle
Selection of any I2C mode, with the SSPEN bit set,
forces the SCL and SDA pins to be open-drain, pro-vided
these pins are programmed to inputs by setting
the appropriate TRISC bits. To ensure proper operation
of the module, pull-up resistors must be provided
externally to the SCL and SDA pins.
9.4.3 SLAVE MODE
In Slave mode, the SCL and SDA pins must be config-ured
as inputs (TRISC<4:3> set). The MSSP module
will override the input state with the output data when
required (slave-transmitter).
The I2C Slave mode hardware will always generate an
interrupt on an address match. Through the mode
select bits, the user can also choose to interrupt on
Start and Stop bits
When an address is matched, or the data transfer after
an address match is received, the hardware automati-cally
will generate the Acknowledge (ACK) pulse and
load the SSPBUF register with the received value
currently in the SSPSR register.
Any combination of the following conditions will cause
the MSSP module not to give this ACK pulse:
• The buffer full bit, BF (SSPSTAT<0>), was set
before the transfer was received.
• The overflow bit, SSPOV (SSPCON<6>), was set
before the transfer was received.
In this case, the SSPSR register value is not loaded
into the SSPBUF, but bit SSPIF (PIR1<3>) is set. The
BF bit is cleared by reading the SSPBUF register, while
bit SSPOV is cleared through software.
The SCL clock input must have a minimum high and
low for proper operation. The high and low times of the
I2C specification, as well as the requirement of the
MSSP module, are shown in timing parameter #100
and parameter #101.
9.4.3.1 Addressing
Once the MSSP module has been enabled, it waits for
a Start condition to occur. Following the Start condition,
the 8 bits are shifted into the SSPSR register. All incom-ing
bits are sampled with the rising edge of the clock
(SCL) line. The value of register SSPSR<7:1> is com-pared
to the value of the SSPADD register. The
address is compared on the falling edge of the eighth
clock (SCL) pulse. If the addresses match, and the BF
and SSPOV bits are clear, the following events occur:
1. The SSPSR register value is loaded into the
SSPBUF register.
2. The Buffer Full bit, BF, is set.
3. An ACK pulse is generated.
4. MSSP Interrupt Flag bit, SSPIF (PIR1<3>), is
set (interrupt is generated if enabled) on the
falling edge of the ninth SCL pulse.
In 10-bit Address mode, two address bytes need to be
received by the slave. The five Most Significant bits
(MSbs) of the first address byte specify if this is a 10-bit
address. Bit R/W (SSPSTAT<2>) must specify a write
so the slave device will receive the second address
byte. For a 10-bit address, the first byte would equal
‘11110 A9 A8 0’, where ‘A9’ and ‘A8’ are the two
MSbs of the address. The sequence of events for
10-bit address is as follows, with steps 7 through 9 for
the slave-transmitter:
1. Receive first (high) byte of address (bits SSPIF,
BF and bit UA (SSPSTAT<1>) are set).
2. Update the SSPADD register with second (low)
byte of address (clears bit UA and releases the
SCL line).
3. Read the SSPBUF register (clears bit BF) and
clear flag bit SSPIF.
4. Receive second (low) byte of address (bits
SSPIF, BF and UA are set).
5. Update the SSPADD register with the first (high)
byte of address. If match releases SCL line, this
will clear bit UA.
7. Receive Repeated Start condition.
8. Receive first (high) byte of address (bits SSPIF
and BF are set).

PIC16F87XA
9.4.3.2 Reception
When the R/W bit of the address byte is clear and an
address match occurs, the R/W bit of the SSPSTAT
register is cleared. The received address is loaded into
the SSPBUF register and the SDA line is held low
(ACK).
When the address byte overflow condition exists, then
the No Acknowledge (ACK) pulse is given. An overflow
condition is defined as either bit BF (SSPSTAT<0>) is
set or bit SSPOV (SSPCON<6>) is set.
An MSSP interrupt is generated for each data transfer
byte. Flag bit SSPIF (PIR1<3>) must be cleared in soft-ware.
The SSPSTAT register is used to determine the
status of the byte.
If SEN is enabled (SSPCON<0> = 1), RC3/SCK/SCL
will be held low (clock stretch) following each data trans-fer.
The clock must be released by setting bit CKP
(SSPCON<4>). See Section 9.4.4 “Clock Stretching”
for more detail.
9.4.3.3 Transmission
When the R/W bit of the incoming address byte is set
and an address match occurs, the R/W bit of the
SSPSTAT register is set. The received address is loaded
into the SSPBUF register. The ACK pulse will be sent on
the ninth bit and pin RC3/SCK/SCL is held low regard-less
of SEN (see Section 9.4.4 “Clock Stretching” for
more detail). By stretching the clock, the master will be
unable to assert another clock pulse until the slave is
done preparing the transmit data. The transmit data
must be loaded into the SSPBUF register, which also
loads the SSPSR register. Then pin RC3/SCK/SCL
should be enabled by setting bit CKP (SSPCON<4>).
The eight data bits are shifted out on the falling edge of
the SCL input. This ensures that the SDA signal is valid
during the SCL high time (Figure 9-9).
The ACK pulse from the master-receiver is latched on
the rising edge of the ninth SCL input pulse. If the SDA
line is high (not ACK), then the data transfer is com-plete.
In this case, when the ACK is latched by the
slave, the slave logic is reset (resets SSPSTAT regis-ter)
and the slave monitors for another occurrence of
the Start bit. If the SDA line was low (ACK), the next
transmit data must be loaded into the SSPBUF register.
Again, pin RC3/SCK/SCL must be enabled by setting
bit CKP.
An MSSP interrupt is generated for each data transfer
byte. The SSPIF bit must be cleared in software and
the SSPSTAT register is used to determine the status
of the byte. The SSPIF bit is set on the falling edge of
the ninth clock pulse.

PIC16F87XA
FIGURE 9-8: I2C SLAVE MODE TIMING WITH SEN = 0 (RECEPTION, 7-BIT ADDRESS)
SDA
SCL
SSPIF
A7 A6 A5 A4 A3 A2 A1 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D1 D0
S 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 7 8 9 P
BF (SSPSTAT<0>)
SSPOV (SSPCON<6>)
R/W = 0 Receiving Data ACK Receiving Data ACK
ACK
Receiving Address
Cleared in software
SSPBUF is read
Bus master
terminates
transfer
SSPOV is set
because SSPBUF is
still full. ACK is not sent.
D2
6
(PIR1<3>)
CKP (CKP does not reset to ‘0’ when SEN = 0)

PIC16F87XA
FIGURE 9-9: I2C SLAVE MODE TIMING (TRANSMISSION, 7-BIT ADDRESS)
SDA
SCL
SSPIF (PIR1<3>)
BF (SSPSTAT<0>)
A6 A5 A4 A3 A2 A1 D6 D5 D4 D3 D2 D1 D0
1 2 3 4 5 6 7 8 2 3 4 5 6 7 8 9
Cleared in software
SSPBUF is written in software
SCL held low
while CPU
responds to SSPIF
From SSPIF ISR
Data in
sampled
S
ACK
R/W = 1 Transmitting Data
ACK
Receiving Address
A7 D7
9 1
Transmitting Data
D6 D5 D4 D3 D2 D1 D0
2 3 4 5 6 7 8 9
Cleared in software
From SSPIF ISR
D7
1
CKP
P
ACK
CKP is set in software CKP is set in software

PIC16F87XA
SDA
SCL
SSPIF
1 1 1 1 0 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D1 D0
Receive Data Byte
D7 D6 D5 D4 D3 D1 D0
S 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 7 8 9 P
BF (SSPSTAT<0>)
Receive Data Byte
ACK
R/W = 0
ACK
Receive First Byte of Address
Cleared in software
D2
6
(PIR1<3>)
Cleared in software
Receive Second Byte of Address
Cleared by hardware
when SSPADD is updated
with low byte of address
UA (SSPSTAT<1>)
Clock is held low until
update of SSPADD has
taken place
UA is set indicating that
the SSPADD needs to be
updated
SSPADD needs to be
updated
Cleared by hardware when
SSPADD is updated with high
byte of address
SSPBUF is written with
contents of SSPSR
Dummy read of SSPBUF
to clear BF flag
ACK
CKP
1 2 3 4 5 7 8 9
Bus master
terminates
transfer
D2
6
ACK
Cleared in software Cleared in software
SSPOV (SSPCON<6>)
SSPOV is set
because SSPBUF is
(CKP does not reset to ‘0’ when SEN = 0)
taken place

PIC16F87XA
FIGURE 9-11: I2C SLAVE MODE TIMING (TRANSMISSION, 10-BIT ADDRESS)
SDA
SCL
SSPIF
1 1 1 1 0 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 1 1 1 1 0 A8
Transmitting Data Byte
D7 D6 D5 D4 D3 D1
ACK
D2
S 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 7 8 9 P
BF (SSPSTAT<0>)
R/W=1
ACK ACK
R/W = 0
ACK
Cleared in software
Bus master
terminates
transfer
A9
6
(PIR1<3>)
SSPADD is updated with low
byte of address
UA (SSPSTAT<1>)
taken place
the SSPADD needs to be
updated
SSPADD needs to be
updated
Sr
Cleared in software
byte of address
contents of SSPSR
to clear BF flag
1 2 3 4 5 6
7 8 9
D0
to clear BF flag
Cleared in software
Write of SSPBUF
initiates transmit
Completion of
clears BF flag
CKP (SSPCON<4>)
CKP is set in software
at the end of the
CKP is automatically cleared in hardware holding SCL low
taken place
data transmission
CKP is set to ‘1’
BF flag is clear
third address sequence

PIC16F87XA
9.4.4 CLOCK STRETCHING
Both 7 and 10-bit Slave modes implement automatic
clock stretching during a transmit sequence.
The SEN bit (SSPCON2<0>) allows clock stretching to
be enabled during receives. Setting SEN will cause
the SCL pin to be held low at the end of each data
receive sequence.
9.4.4.1 Clock Stretching for 7-bit Slave
Receive Mode (SEN = 1)
In 7-bit Slave Receive mode, on the falling edge of the
ninth clock at the end of the ACK sequence, if the BF
bit is set, the CKP bit in the SSPCON register is
automatically cleared, forcing the SCL output to be
held low. The CKP bit being cleared to ‘0’ will assert
the SCL line low. The CKP bit must be set in the user’s
ISR before reception is allowed to continue. By holding
the SCL line low, the user has time to service the ISR
and read the contents of the SSPBUF before the
master device can initiate another receive sequence.
This will prevent buffer overruns from occurring (see
Figure 9-13).
Note 1: If the user reads the contents of the
SSPBUF before the falling edge of the
ninth clock, thus clearing the BF bit, the
CKP bit will not be cleared and clock
stretching will not occur.
2: The CKP bit can be set in software
regardless of the state of the BF bit. The
user should be careful to clear the BF bit
in the ISR before the next receive
sequence in order to prevent an overflow
condition.
Receive Mode (SEN = 1)
In 10-bit Slave Receive mode, during the address
sequence, clock stretching automatically takes place
but CKP is not cleared. During this time, if the UA bit is
set after the ninth clock, clock stretching is initiated.
The UA bit is set after receiving the upper byte of the
10-bit address and following the receive of the second
byte of the 10-bit address, with the R/W bit cleared to
‘0’. The release of the clock line occurs upon updating
SSPADD. Clock stretching will occur on each data
receive sequence as described in 7-bit mode.
Transmit Mode
7-bit Slave Transmit mode implements clock stretching
by clearing the CKP bit after the falling edge of the ninth
clock, if the BF bit is clear. This occurs regardless of the
state of the SEN bit.
The user’s ISR must set the CKP bit before transmis-sion
is allowed to continue. By holding the SCL line
low, the user has time to service the ISR and load the
contents of the SSPBUF before the master device can
initiate another transmit sequence (see Figure 9-9).
Note 1: If the user loads the contents of SSPBUF,
setting the BF bit before the falling edge of
the ninth clock, the CKP bit will not be
cleared and clock stretching will not occur.
2: The CKP bit can be set in software
regardless of the state of the BF bit.
Transmit Mode
In 10-bit Slave Transmit mode, clock stretching is con-trolled
during the first two address sequences by the
state of the UA bit, just as it is in 10-bit Slave Receive
mode. The first two addresses are followed by a third
address sequence, which contains the high order bits
of the 10-bit address and the R/W bit set to ‘1’. After
the third address sequence is performed, the UA bit is
not set, the module is now configured in Transmit
mode and clock stretching is controlled by the BF flag
as in 7-bit Slave Transmit mode (see Figure 9-11).
Note: If the user polls the UA bit and clears it by
updating the SSPADD register before the
falling edge of the ninth clock occurs and if
the user hasn’t cleared the BF bit by read-ing
the SSPBUF register before that time,
then the CKP bit will still NOT be asserted
low. Clock stretching, on the basis of the
state of the BF bit, only occurs during a
data sequence, not an address sequence.

PIC16F87XA
9.4.4.5 Clock Synchronization and the
CKP Bit
When the CKP bit is cleared, the SCL output is forced
to ‘0’; however, setting the CKP bit will not assert the
SCL output low until the SCL output is already sampled
low. Therefore, the CKP bit will not assert the SCL line
until an external I2C master device has already
asserted the SCL line. The SCL output will remain low
until the CKP bit is set and all other devices on the I2C
bus have deasserted SCL. This ensures that a write to
the CKP bit will not violate the minimum high time
requirement for SCL (see Figure 9-12).
FIGURE 9-12: CLOCK SYNCHRONIZATION TIMING
SDA
SCL
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
DX DX-1
CKP
WR
SSPCON
Master device
deasserts clock
Master device
asserts clock

PIC16F87XA
SDA
SCL
SSPIF
A7 A6 A5 A4 A3 A2 A1 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D1 D0
S 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 7 8 9 P
BF (SSPSTAT<0>)
SSPOV (SSPCON<6>)
R/W = 0 Receiving Data ACK Receiving Data ACK
ACK
Receiving Address
Cleared in software
SSPBUF is read
Bus master
terminates
transfer
SSPOV is set
because SSPBUF is
D2
6
(PIR1<3>)
CKP
CKP
written
to ‘1’ in
If BF is cleared
prior to the falling
edge of the 9th clock,
CKP will not be reset
to ‘0’ and no clock
stretching will occur
software
Clock is not held low
because buffer full bit is
clear prior to falling edge
of 9th clock
because ACK = 1
BF is set after falling
edge of the 9th clock,
CKP is reset to ‘0’ and
clock stretching occurs

PIC16F87XA
FIGURE 9-14: I2C SLAVE MODE TIMING SEN = 1 (RECEPTION, 10-BIT ADDRESS)
SDA
SCL
SSPIF
taken place
1 1 1 1 0 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D1 D0
Receive Data Byte
D7 D6 D5 D4 D3 D1 D0
S 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 7 8 9 P
BF (SSPSTAT<0>)
Receive Data Byte
ACK
R/W = 0
ACK
Cleared in software
D2
6
(PIR1<3>)
Cleared in software
SSPADD is updated with low
byte of address after falling edge
UA (SSPSTAT<1>)
taken place
SSPADD needs to be
updated
of ninth clock of ninth clock
SSPADD needs to be
updated
byte of address after falling edge
contents of SSPSR
to clear BF flag
ACK
CKP
1 2 3 4 5 7 8 9
Bus master
terminates
transfer
D2
6
ACK
SSPOV (SSPCON<6>)
CKP written to ‘1’
Note:An update of the SSPADD register
before the falling edge of the ninth clock
will have no effect on UA, and UA will
remain set.
Note:An update of the SSPADD register
before the falling edge of the ninth clock
will have no effect on UA and UA will
remain set. in software
SSPOV is set
because SSPBUF is
to clear BF flag
because ACK = 1

PIC16F87XA
9.4.5 GENERAL CALL ADDRESS
SUPPORT
The addressing procedure for the I2C bus is such that
the first byte after the Start condition usually determines
which device will be the slave addressed by the master.
The exception is the general call address which can
address all devices. When this address is used, all
devices should, in theory, respond with an Acknowledge.
The general call address is one of eight addresses
reserved for specific purposes by the I2C protocol. It
consists of all ‘0’s with R/W = 0.
The general call address is recognized when the Gen-eral
Call Enable bit (GCEN) is enabled (SSPCON2<7>
set). Following a Start bit detect, 8 bits are shifted into
the SSPSR and the address is compared against the
SSPADD. It is also compared to the general call
address and fixed in hardware.
If the general call address matches, the SSPSR is
transferred to the SSPBUF, the BF flag bit is set (eighth
bit) and on the falling edge of the ninth bit (ACK bit), the
SSPIF interrupt flag bit is set.
When the interrupt is serviced, the source for the inter-rupt
can be checked by reading the contents of the
SSPBUF. The value can be used to determine if the
address was device specific or a general call address.
In 10-bit mode, the SSPADD is required to be updated
for the second half of the address to match and the UA
bit is set (SSPSTAT<1>). If the general call address is
sampled when the GCEN bit is set, while the slave is
configured in 10-bit Address mode, then the second
half of the address is not necessary, the UA bit will not
be set and the slave will begin receiving data after the
Acknowledge (Figure 9-15).
FIGURE 9-15: SLAVE MODE GENERAL CALL ADDRESS SEQUENCE
(7 OR 10-BIT ADDRESS MODE)
SDA
SCL
S
SSPIF
BF (SSPSTAT<0>)
SSPOV (SSPCON<6>)
Address is compared to general call address.
After ACK, set interrupt.
Receiving Data ACK
D7 D6 D5 D4 D3 D2 D1 D0
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
Cleared in software
SSPBUF is read
R/W = 0
General Call Address ACK
GCEN (SSPCON2<7>)
‘0’
‘1’

PIC16F87XA
9.4.6 MASTER MODE
Master mode is enabled by setting and clearing the
appropriate SSPM bits in SSPCON and by setting the
SSPEN bit. In Master mode, the SCL and SDA lines
are manipulated by the MSSP hardware.
Master mode of operation is supported by interrupt
generation on the detection of the Start and Stop con-ditions.
The Stop (P) and Start (S) bits are cleared from
a Reset or when the MSSP module is disabled. Control
of the I2C bus may be taken when the P bit is set or the
bus is Idle, with both the S and P bits clear.
In Firmware Controlled Master mode, user code
conducts all I2C bus operations based on Start and
Stop bit conditions.
Once Master mode is enabled, the user has six
options.
1. Assert a Start condition on SDA and SCL.
2. Assert a Repeated Start condition on SDA and
SCL.
3. Write to the SSPBUF register, initiating
transmission of data/address.
4. Configure the I2C port to receive data.
5. Generate an Acknowledge condition at the end
of a received byte of data.
6. Generate a Stop condition on SDA and SCL.
Note: The MSSP module, when configured in
I2C Master mode, does not allow queueing
of events. For instance, the user is not
allowed to initiate a Start condition and
immediately write the SSPBUF register to
initiate transmission before the Start condi-tion
is complete. In this case, the SSPBUF
will not be written to and the WCOL bit will
be set, indicating that a write to the
SSPBUF did not occur.
The following events will cause SSP Interrupt Flag bit,
SSPIF, to be set (SSP interrupt if enabled):
• Start condition
• Stop condition
• Data transfer byte transmitted/received
• Acknowledge transmit
• Repeated Start
FIGURE 9-16: MSSP BLOCK DIAGRAM (I2C MASTER MODE)
Internal
Data Bus
Read Write
SSPBUF
SSPSR
MSb LSb
Start bit, Stop bit,
Acknowledge
Generate
Start bit Detect
Clock Cntl
SSPM3:SSPM0
SSPADD<6:0>
Baud
Rate
Generator
Clock Arbitrate/WCOL Detect
(hold off clock source)
Set/Reset, S, P, WCOL (SSPSTAT)
Shift
Clock
SDA
Stop bit Detect
Write Collision Detect
Clock Arbitration
State Counter for
end of XMIT/RCV
SCL
SDA In
Receive Enable
SCL In
Bus Collision
Set SSPIF, BCLIF
Reset ACKSTAT, PEN (SSPCON2)

PIC16F87XA
9.4.6.1 I2C Master Mode Operation
The master device generates all of the serial clock
pulses and the Start and Stop conditions. A transfer is
ended with a Stop condition or with a Repeated Start
condition. Since the Repeated Start condition is also
the beginning of the next serial transfer, the I2C bus will
not be released.
In Master Transmitter mode, serial data is output
through SDA while SCL outputs the serial clock. The
first byte transmitted contains the slave address of the
receiving device (7 bits) and the Read/Write (R/W) bit.
In this case, the R/W bit will be logic ‘0’. Serial data is
transmitted 8 bits at a time. After each byte is transmit-ted,
an Acknowledge bit is received. Start and Stop
conditions are output to indicate the beginning and the
end of a serial transfer.
In Master Receive mode, the first byte transmitted con-tains
the slave address of the transmitting device
(7 bits) and the R/W bit. In this case, the R/W bit will be
logic ‘1’. Thus, the first byte transmitted is a 7-bit slave
address followed by a ‘1’ to indicate the receive bit.
Serial data is received via SDA while SCL outputs the
serial clock. Serial data is received 8 bits at a time. After
each byte is received, an Acknowledge bit is transmit-ted.
Start and Stop conditions indicate the beginning
and end of transmission.
The baud rate generator used for the SPI mode opera-tion
is used to set the SCL clock frequency for either
100 kHz, 400 kHz or 1 MHz I2C operation. See
Section 9.4.7 “Baud Rate Generator” for more detail.
A typical transmit sequence would go as follows:
1. The user generates a Start condition by setting
the Start Enable bit, SEN (SSPCON2<0>).
2. SSPIF is set. The MSSP module will wait the
required Start time before any other operation
takes place.
3. The user loads the SSPBUF with the slave
address to transmit.
4. Address is shifted out the SDA pin until all 8 bits
are transmitted.
5. The MSSP module shifts in the ACK bit from the
slave device and writes its value into the
SSPCON2 register (SSPCON2<6>).
6. The MSSP module generates an interrupt at the
end of the ninth clock cycle by setting the SSPIF
bit.
7. The user loads the SSPBUF with eight bits of
data.
8. Data is shifted out the SDA pin until all 8 bits are
transmitted.
9. The MSSP module shifts in the ACK bit from the
slave device and writes its value into the
SSPCON2 register (SSPCON2<6>).
10. The MSSP module generates an interrupt at the
end of the ninth clock cycle by setting the SSPIF
bit.
11. The user generates a Stop condition by setting
the Stop Enable bit, PEN (SSPCON2<2>).
12. Interrupt is generated once the Stop condition is
complete.

PIC16F87XA
9.4.7 BAUD RATE GENERATOR
In I2C Master mode, the Baud Rate Generator (BRG)
reload value is placed in the lower 7 bits of the
SSPADD register (Figure 9-17). When a write occurs to
SSPBUF, the Baud Rate Generator will automatically
begin counting. The BRG counts down to 0 and stops
until another reload has taken place. The BRG count is
decremented twice per instruction cycle (TCY) on the
Q2 and Q4 clocks. In I2C Master mode, the BRG is
reloaded automatically.
Once the given operation is complete (i.e., transmis-sion
of the last data bit is followed by ACK), the internal
clock will automatically stop counting and the SCL pin
will remain in its last state.
Table 9-3 demonstrates clock rates based on
instruction cycles and the BRG value loaded into
SSPADD.
FIGURE 9-17: BAUD RATE GENERATOR BLOCK DIAGRAM
SSPM3:SSPM0
SSPM3:SSPM0
SCL
Reload
Control
TABLE 9-3: I2C CLOCK RATE W/BRG
SSPADD<6:0>
Reload
CLKO BRG Down Counter FOSC/4
FCY FCY*2 BRG Value
FSCL
(2 Rollovers of BRG)
10 MHz 20 MHz 19h 400 kHz(1)
10 MHz 20 MHz 20h 312.5 kHz
10 MHz 20 MHz 3Fh 100 kHz
4 MHz 8 MHz 0Ah 400 kHz(1)
4 MHz 8 MHz 0Dh 308 kHz
4 MHz 8 MHz 28h 100 kHz
1 MHz 2 MHz 03h 333 kHz(1)
1 MHz 2 MHz 0Ah 100 kHz
1 MHz 2 MHz 00h 1 MHz(1)
Note 1: The I2C interface does not conform to the 400 kHz I2C specification (which applies to rates greater than
100 kHz) in all details, but may be used with care where higher rates are required by the application.

PIC16F87XA
9.4.7.1 Clock Arbitration
Clock arbitration occurs when the master, during any
receive, transmit or Repeated Start/Stop condition,
deasserts the SCL pin (SCL allowed to float high).
When the SCL pin is allowed to float high, the Baud
Rate Generator (BRG) is suspended from counting
until the SCL pin is actually sampled high. When the
SCL pin is sampled high, the Baud Rate Generator is
reloaded with the contents of SSPADD<6:0> and
begins counting. This ensures that the SCL high time
will always be at least one BRG rollover count, in the
event that the clock is held low by an external device
(Figure 9-17).
FIGURE 9-18: BAUD RATE GENERATOR TIMING WITH CLOCK ARBITRATION
SDA
SCL
DX DX-1
SCL deasserted but slave holds
BRG
Value
BRG
SCL low (clock arbitration)
SCL allowed to transition high
BRG decrements on
Q2 and Q4 cycles
03h 02h 01h 00h (hold off) 03h 02h
SCL is sampled high, reload takes
place and BRG starts its count
Reload

PIC16F87XA
9.4.8 I2C MASTER MODE START
CONDITION TIMING
To initiate a Start condition, the user sets the Start con-dition
enable bit, SEN (SSPCON2<0>). If the SDA and
SCL pins are sampled high, the Baud Rate Generator
is reloaded with the contents of SSPADD<6:0> and
starts its count. If SCL and SDA are both sampled high
when the Baud Rate Generator times out (TBRG), the
SDA pin is driven low. The action of the SDA being
driven low, while SCL is high, is the Start condition and
causes the S bit (SSPSTAT<3>) to be set. Following
this, the Baud Rate Generator is reloaded with the con-tents
of SSPADD<6:0> and resumes its count. When
the Baud Rate Generator times out (TBRG), the SEN bit
(SSPCON2<0>) will be automatically cleared by hard-ware,
the Baud Rate Generator is suspended, leaving
the SDA line held low and the Start condition is
complete.
9.4.8.1 WCOL Status Flag
If the user writes the SSPBUF when a Start sequence
is in progress, the WCOL is set and the contents of the
buffer are unchanged (the write doesn’t occur).
Note: If at the beginning of the Start condition,
the SDA and SCL pins are already sam-pled
low, or if during the Start condition, the
SCL line is sampled low before the SDA
line is driven low, a bus collision occurs,
the Bus Collision Interrupt Flag (BCLIF) is
set, the Start condition is aborted and the
I2C module is reset into its Idle state.
FIGURE 9-19: FIRST START BIT TIMING
Note: Because queueing of events is not
allowed, writing to the lower 5 bits of
SSPCON2 is disabled until the Start
condition is complete.
Write to SEN bit occurs here
SDA
SCL
Set S bit (SSPSTAT<3>)
SDA = 1,
SCL = At completion of Start bit, 1
hardware clears SEN bit
and sets SSPIF bit
TBRG Write to SSPBUF occurs here
S
1st Bit 2nd Bit
TBRG
TBRG
TBRG

PIC16F87XA
9.4.9 I2C MASTER MODE REPEATED
START CONDITION TIMING
A Repeated Start condition occurs when the RSEN bit
(SSPCON2<1>) is programmed high and the I2C logic
module is in the Idle state. When the RSEN bit is set,
the SCL pin is asserted low. When the SCL pin is sam-pled
low, the Baud Rate Generator is loaded with the
contents of SSPADD<5:0> and begins counting. The
SDA pin is released (brought high) for one Baud Rate
Generator count (TBRG). When the Baud Rate Genera-tor
times out, if SDA is sampled high, the SCL pin will
be deasserted (brought high). When SCL is sampled
high, the Baud Rate Generator is reloaded with the
contents of SSPADD<6:0> and begins counting. SDA
and SCL must be sampled high for one TBRG. This
action is then followed by assertion of the SDA pin
(SDA = 0) for one TBRG while SCL is high. Following
this, the RSEN bit (SSPCON2<1>) will be automatically
cleared and the Baud Rate Generator will not be
reloaded, leaving the SDA pin held low. As soon as a
Start condition is detected on the SDA and SCL pins,
the S bit (SSPSTAT<3>) will be set. The SSPIF bit will
not be set until the Baud Rate Generator has timed out.
Immediately following the SSPIF bit getting set, the user
may write the SSPBUF with the 7-bit address in 7-bit
mode or the default first address in 10-bit mode. After
the first eight bits are transmitted and an ACK is
received, the user may then transmit an additional eight
bits of address (10-bit mode) or eight bits of data (7-bit
mode).
If the user writes the SSPBUF when a Repeated Start
sequence is in progress, the WCOL is set and the con-tents
of the buffer are unchanged (the write doesn’t
occur).
Note 1: If RSEN is programmed while any other
event is in progress, it will not take effect.
2: A bus collision during the Repeated Start
condition occurs if:
• SDA is sampled low when SCL goes
from low to high.
• SCL goes low before SDA is
asserted low. This may indicate that
another master is attempting to
transmit a data ‘1’.
Note: Because queueing of events is not
FIGURE 9-20: REPEAT START CONDITION WAVEFORM
allowed, writing of the lower 5 bits of
SSPCON2 is disabled until the Repeated
Start condition is complete.
SDA
Set S (SSPSTAT<3>)
At completion of Start bit,
hardware clears RSEN bit
and sets SSPIF
1st Bit
occurs here,
SDA = 1,
SDA = 1,
SCL (no change)
SCL = 1
TBRG TBRG TBRG
Falling edge of ninth clock, Write to SSPBUF occurs here
SCL
TBRG
Sr = Repeated Start
Write to SSPCON2
end of Xmit
TBRG

PIC16F87XA
9.4.10 I2C MASTER MODE
TRANSMISSION
Transmission of a data byte, a 7-bit address or the
other half of a 10-bit address is accomplished by simply
writing a value to the SSPBUF register. This action will
set the Buffer Full flag bit, BF, and allow the Baud Rate
Generator to begin counting and start the next trans-mission.
Each bit of address/data will be shifted out
onto the SDA pin after the falling edge of SCL is
asserted (see data hold time specification, parameter
#106). SCL is held low for one Baud Rate Generator
rollover count (TBRG). Data should be valid before SCL
is released high (see data setup time specification,
parameter #107). When the SCL pin is released high, it
is held that way for TBRG. The data on the SDA pin
must remain stable for that duration and some hold
time after the next falling edge of SCL. After the eighth
bit is shifted out (the falling edge of the eighth clock),
the BF flag is cleared and the master releases SDA.
This allows the slave device being addressed to
respond with an ACK bit during the ninth bit time, if an
address match occurred or if data was received prop-erly.
The status of ACK is written into the ACKDT bit on
the falling edge of the ninth clock. If the master receives
an Acknowledge, the Acknowledge Status bit,
ACKSTAT, is cleared. If not, the bit is set. After the ninth
clock, the SSPIF bit is set and the master clock (Baud
Rate Generator) is suspended until the next data byte
is loaded into the SSPBUF, leaving SCL low and SDA
unchanged (Figure 9-21).
After the write to the SSPBUF, each bit of address will
be shifted out on the falling edge of SCL, until all seven
address bits and the R/W bit are completed. On the fall-ing
edge of the eighth clock, the master will deassert
the SDA pin, allowing the slave to respond with an
Acknowledge. On the falling edge of the ninth clock, the
master will sample the SDA pin to see if the address
was recognized by a slave. The status of the ACK bit is
loaded into the ACKSTAT status bit (SSPCON2<6>).
Following the falling edge of the ninth clock transmis-sion
of the address, the SSPIF is set, the BF flag is
cleared and the Baud Rate Generator is turned off until
another write to the SSPBUF takes place, holding SCL
low and allowing SDA to float.
9.4.10.1 BF Status Flag
In Transmit mode, the BF bit (SSPSTAT<0>) is set
when the CPU writes to SSPBUF and is cleared when
all eight bits are shifted out.
If the user writes the SSPBUF when a transmit is
already in progress (i.e., SSPSR is still shifting out a
data byte), the WCOL is set and the contents of the
buffer are unchanged (the write doesn’t occur).
WCOL must be cleared in software.
9.4.10.3 ACKSTAT Status Flag
In Transmit mode, the ACKSTAT bit (SSPCON2<6>) is
cleared when the slave has sent an Acknowledge
(ACK = 0) and is set when the slave does Not Acknowl-edge
(ACK = 1). A slave sends an Acknowledge when
it has recognized its address (including a general call)
or when the slave has properly received its data.
9.4.11 I2C MASTER MODE RECEPTION
Master mode reception is enabled by programming the
Receive Enable bit, RCEN (SSPCON2<3>).
Note: The MSSP module must be in an Idle state
before the RCEN bit is set or the RCEN bit
will be disregarded.
The Baud Rate Generator begins counting and on each
rollover, the state of the SCL pin changes (high to low/
low to high) and data is shifted into the SSPSR. After the
falling edge of the eighth clock, the receive enable flag
is automatically cleared, the contents of the SSPSR are
loaded into the SSPBUF, the BF flag bit is set, the
SSPIF flag bit is set and the Baud Rate Generator is
suspended from counting, holding SCL low. The MSSP
is now in Idle state, awaiting the next command. When
the buffer is read by the CPU, the BF flag bit is automat-ically
cleared. The user can then send an Acknowledge
bit at the end of reception by setting the Acknowledge
Sequence Enable bit, ACKEN (SSPCON2<4>).
9.4.11.1 BF Status Flag
In receive operation, the BF bit is set when an address
or data byte is loaded into SSPBUF from SSPSR. It is
cleared when the SSPBUF register is read.
9.4.11.2 SSPOV Status Flag
In receive operation, the SSPOV bit is set when 8 bits
are received into the SSPSR and the BF flag bit is
already set from a previous reception.
If the user writes the SSPBUF when a receive is
already in progress (i.e., SSPSR is still shifting in a data
byte), the WCOL bit is set and the contents of the buffer
are unchanged (the write doesn’t occur).

PIC16F87XA
FIGURE 9-21: I2C MASTER MODE WAVEFORM (TRANSMISSION, 7 OR 10-BIT ADDRESS)
SDA
SCL
SSPIF
BF (SSPSTAT<0>)
SEN
A7 A6 A5 A4 A3 A2 A1 ACK = 0 D7 D6 D5 D4 D3 D2 D1 D0
ACK
Transmitting Data or Second Half
Transmit Address to Slave R/W = 0
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 P
Cleared in software service routine
from SSP interrupt
After Start condition, SEN cleared by hardware
S
SSPBUF written with 7-bit address and R/W.
Start transmit.
SCL held low
while CPU
responds to SSPIF
SEN = 0
of 10-bit Address
Write SSPCON2<0> SEN = 1
Start condition begins
From Slave, clear ACKSTAT bit SSPCON2<6>
ACKSTAT in
SSPCON2 = 1
Cleared in software
SSPBUF written
PEN
Cleared in software
R/W

PIC16F87XA
FIGURE 9-22: I2C MASTER MODE WAVEFORM (RECEPTION, 7-BIT ADDRESS)
Set ACKEN, start Acknowledge sequence,
P
Write to SSPCON2<4>
to start Acknowledge sequence,
SDA = ACKDT (SSPCON2<5>) = 0
Master configured as a receiver
by programming SSPCON2<3> (RCEN = 1)
RCEN cleared
automatically
Receiving Data from Slave Receiving Data from Slave
SDA = ACKDT = 1
D7 D6 D5 D4 D3 D2 D1 D0
5 6 7 8 9
begin Start condition
start XMIT
Transmit Address to Slave R/W = 1
SDA A7 A6 A5 A4 A3 A2 A1
SCL 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4
S
Bus master
terminates
transfer
ACK
ACK D7 D6 D5 D4 D3 D2 D1 D0
SSPIF
SDA = 0, SCL = 1
while CPU
BF
ACK is not sent
Write to SSPCON2<0> (SEN = 1),
Write to SSPBUF occurs here,
ACK from Slave
PEN bit = 1
written here
Data shifted in on falling edge of CLK
Cleared in software
SEN = 0
(SSPSTAT<0>)
SSPOV
ACK
Last bit is shifted into SSPSR and
contents are unloaded into SSPBUF
Set SSPIF interrupt
at end of receive
Set P bit
(SSPSTAT<4>)
and SSPIF
Cleared in
software
ACK from master
Set SSPIF at end
Set SSPIF interrupt
at end of Acknowledge
sequence
Set SSPIF interrupt
at end of Acknow-ledge
sequence
of receive
SSPOV is set because
SSPBUF is still full
RCEN = 1, start
next receive
RCEN cleared
automatically
responds to SSPIF
ACKEN
Cleared in software
SDA = ACKDT = 0

PIC16F87XA
9.4.12 ACKNOWLEDGE SEQUENCE
TIMING
An Acknowledge sequence is enabled by setting the
Acknowledge Sequence Enable bit, ACKEN
(SSPCON2<4>). When this bit is set, the SCL pin is
pulled low and the contents of the Acknowledge data bit
are presented on the SDA pin. If the user wishes to gen-erate
an Acknowledge, then the ACKDT bit should be
cleared. If not, the user should set the ACKDT bit before
starting an Acknowledge sequence. The Baud Rate
Generator then counts for one rollover period (TBRG)
and the SCL pin is deasserted (pulled high). When the
SCL pin is sampled high (clock arbitration), the Baud
Rate Generator counts for TBRG. The SCL pin is then
pulled low. Following this, the ACKEN bit is automatically
cleared, the baud rate generator is turned off and the
MSSP module then goes into Idle mode (Figure 9-23).
If the user writes the SSPBUF when an Acknowledge
sequence is in progress, then WCOL is set and the
contents of the buffer are unchanged (the write doesn’t
occur).
9.4.13 STOP CONDITION TIMING
A Stop bit is asserted on the SDA pin at the end of a
receive/transmit by setting the Stop Sequence Enable
bit, PEN (SSPCON2<2>). At the end of a receive/
transmit, the SCL line is held low after the falling edge
of the ninth clock. When the PEN bit is set, the master
will assert the SDA line low. When the SDA line is sam-pled
low, the Baud Rate Generator is reloaded and
counts down to 0. When the Baud Rate Generator
times out, the SCL pin will be brought high and one
TBRG (Baud Rate Generator rollover count) later, the
SDA pin will be deasserted. When the SDA pin is sam-pled
high while SCL is high, the P bit (SSPSTAT<4>) is
set. A TBRG later, the PEN bit is cleared and the SSPIF
bit is set (Figure 9-24).
If the user writes the SSPBUF when a Stop sequence
is in progress, then the WCOL bit is set and the con-tents
of the buffer are unchanged (the write doesn’t
occur).
FIGURE 9-23: ACKNOWLEDGE SEQUENCE WAVEFORM
Acknowledge sequence starts here,
SDA
SCL
write to SSPCON2
ACKEN = 1, ACKDT = 0
D0
8
Set SSPIF at the end
TBRG TBRG
ACK
Cleared in
of receive
SSPIF
Cleared in
software
software Set SSPIF at the end
Note: TBRG = one Baud Rate Generator period.
ACKEN automatically cleared
9
of Acknowledge sequence
FIGURE 9-24: STOP CONDITION RECEIVE OR TRANSMIT MODE
SCL
SDA
SCL = 1 for TBRG, followed by SDA = 1 for TBRG
after SDA sampled high. P bit (SSPSTAT<4>) is set.
P
TBRG TBRG
PEN bit (SSPCON2<2>) is cleared by
hardware and the SSPIF bit is set
SCL brought high after TBRG
TBRG
TBRG
SDA asserted low before rising edge of clock
Write to SSPCON2,
set PEN
Falling edge of
9th clock
to setup Stop condition
ACK
Note: TBRG = one Baud Rate Generator period.

PIC16F87XA
9.4.14 SLEEP OPERATION
While in Sleep mode, the I2C module can receive
addresses or data and when an address match or com-plete
byte transfer occurs, wake the processor from
Sleep (if the MSSP interrupt is enabled).
9.4.15 EFFECT OF A RESET
A Reset disables the MSSP module and terminates the
current transfer.
9.4.16 MULTI-MASTER MODE
In Multi-Master mode, the interrupt generation on the
detection of the Start and Stop conditions allows the
determination of when the bus is free. The Stop (P) and
Start (S) bits are cleared from a Reset or when the
MSSP module is disabled. Control of the I2C bus may
be taken when the P bit (SSPSTAT<4>) is set, or the
bus is Idle, with both the S and P bits clear. When the
bus is busy, enabling the SSP interrupt will generate
the interrupt when the Stop condition occurs.
In multi-master operation, the SDA line must be
monitored for arbitration to see if the signal level is at
the expected output level. This check is performed in
hardware with the result placed in the BCLIF bit.
The states where arbitration can be lost are:
• Address Transfer
• Data Transfer
• A Start Condition
• A Repeated Start Condition
• An Acknowledge Condition
9.4.17 MULTI -MASTER COMMUNICATION,
BUS COLLISION AND BUS
ARBITRATION
Multi-Master mode support is achieved by bus arbitra-tion.
When the master outputs address/data bits onto
the SDA pin, arbitration takes place when the master
outputs a ‘1’ on SDA by letting SDA float high and
another master asserts a ‘0’. When the SCL pin floats
high, data should be stable. If the expected data on
SDA is a ‘1’ and the data sampled on the SDA pin = 0,
then a bus collision has taken place. The master will set
the Bus Collision Interrupt Flag, BCLIF, and reset the
I2C port to its Idle state (Figure 9-25).
If a transmit was in progress when the bus collision
occurred, the transmission is halted, the BF flag is
cleared, the SDA and SCL lines are deasserted and the
SSPBUF can be written to. When the user services the
bus collision Interrupt Service Routine and if the I2C
bus is free, the user can resume communication by
asserting a Start condition.
If a Start, Repeated Start, Stop or Acknowledge condition
was in progress when the bus collision occurred, the con-dition
is aborted, the SDA and SCL lines are deasserted
and the respective control bits in the SSPCON2 register
are cleared. When the user services the bus collision
Interrupt Service Routine and if the I2C bus is free, the
user can resume communication by asserting a Start
condition.
The Master will continue to monitor the SDA and SCL
pins. If a Stop condition occurs, the SSPIF bit will be set.
A write to the SSPBUF will start the transmission of
data at the first data bit regardless of where the
transmitter left off when the bus collision occurred.
In Multi-Master mode, the interrupt generation on the
detection of Start and Stop conditions allows the determi-nation
of when the bus is free. Control of the I2C bus can
be taken when the P bit is set in the SSPSTAT register or
the bus is Idle and the S and P bits are cleared.
FIGURE 9-25: BUS COLLISION TIMING FOR TRANSMIT AND ACKNOWLEDGE
SDA
SCL
BCLIF
SDA line pulled low
by another source
SDA released
Sample SDA. While SCL is high,
data doesn’t match what is driven
by the master. Bus collision has occurred.
Set bus collision
interrupt (BCLIF)
by master
Data changes
while SCL = 0

PIC16F87XA
9.4.17.1 Bus Collision During a Start
Condition
During a Start condition, a bus collision occurs if:
a) SDA or SCL are sampled low at the beginning of
the Start condition (Figure 9-26).
b) SCL is sampled low before SDA is asserted low
(Figure 9-27).
During a Start condition, both the SDA and the SCL
pins are monitored.
If the SDA pin is already low, or the SCL pin is already
low, then all of the following occur:
• the Start condition is aborted,
• the BCLIF flag is set and
• the MSSP module is reset to its Idle state
(Figure 9-26).
The Start condition begins with the SDA and SCL pins
deasserted. When the SDA pin is sampled high, the
Baud Rate Generator is loaded from SSPADD<6:0>
and counts down to 0. If the SCL pin is sampled low
while SDA is high, a bus collision occurs because it is
assumed that another master is attempting to drive a
data ‘1’ during the Start condition.
If the SDA pin is sampled low during this count, the
BRG is reset and the SDA line is asserted early
(Figure 9-28). If, however, a ‘1’ is sampled on the SDA
pin, the SDA pin is asserted low at the end of the BRG
count. The Baud Rate Generator is then reloaded and
counts down to 0 and during this time, if the SCL pin is
sampled as ‘0’, a bus collision does not occur. At the
end of the BRG count, the SCL pin is asserted low.
Note: The reason that bus collision is not a factor
during a Start condition is that no two bus
masters can assert a Start condition at the
exact same time. Therefore, one master
will always assert SDA before the other.
This condition does not cause a bus colli-sion
because the two masters must be
allowed to arbitrate the first address fol-lowing
the Start condition. If the address is
the same, arbitration must be allowed to
continue into the data portion, Repeated
Start or Stop conditions.
FIGURE 9-26: BUS COLLISION DURING START CONDITION (SDA ONLY)
SDA
SCL
SEN
SDA goes low before the SEN bit is set.
S bit and SSPIF set because
Set BCLIF,
SDA = 0, SCL = 1.
Set SEN, enable Start
condition if SDA = 1, SCL = 1
SDA sampled low before
SEN cleared automatically because of bus collision.
SSP module reset into Idle state.
Start condition. Set BCLIF.
S bit and SSPIF set because
BCLIF
S
SSPIF
SDA = 0, SCL = 1.
SSPIF and BCLIF are
cleared in software
SSPIF and BCLIF are
cleared in software

PIC16F87XA
FIGURE 9-27: BUS COLLISION DURING START CONDITION (SCL = 0)
SDA
SCL
SEN
SCL = 0 before SDA = 0,
bus collision occurs. Set BCLIF.
SDA = 0, SCL = 1
TBRG TBRG
sequence if SDA = 1, SCL = 1
BCLIF
S
SSPIF
Interrupt cleared
in software
SCL = 0 before BRG time-out,
bus collision occurs. Set BCLIF.
‘0’ ‘0’
‘0’ ‘0’
FIGURE 9-28: BRG RESET DUE TO SDA ARBITRATION DURING START CONDITION
SDA
SCL
SEN
Set S
SDA = 0, SCL = 1
Less than TBRG
TBRG
BCLIF
S
SSPIF
S
Set SSPIF
SCL pulled low after BRG
time-out
‘0’
Interrupts cleared
sequence if SDA = 1, SCL = 1
SDA = 0, SCL = 1,
set SSPIF in software
SDA pulled low by other master.
Reset BRG and assert SDA.

PIC16F87XA
9.4.17.2 Bus Collision During a Repeated
Start Condition
During a Repeated Start condition, a bus collision
occurs if:
a) A low level is sampled on SDA when SCL goes
from low level to high level.
b) SCL goes low before SDA is asserted low,
indicating that another master is attempting to
transmit a data ‘1’.
When the user deasserts SDA and the pin is allowed to
float high, the BRG is loaded with SSPADD<6:0> and
counts down to 0. The SCL pin is then deasserted and
when sampled high, the SDA pin is sampled.
If SDA is low, a bus collision has occurred (i.e., another
master is attempting to transmit a data ‘0’, see
Figure 9-29). If SDA is sampled high, the BRG is
reloaded and begins counting. If SDA goes from high to
low before the BRG times out, no bus collision occurs
because no two masters can assert SDA at exactly the
same time.
If SCL goes from high to low before the BRG times out
and SDA has not already been asserted, a bus collision
occurs. In this case, another master is attempting to
transmit a data ‘1’ during the Repeated Start condition
(Figure 9-30).
If at the end of the BRG time-out, both SCL and SDA
are still high, the SDA pin is driven low and the BRG is
reloaded and begins counting. At the end of the count,
regardless of the status of the SCL pin, the SCL pin is
driven low and the Repeated Start condition is
complete.
FIGURE 9-29: BUS COLLISION DURING A REPEATED START CONDITION (CASE 1)
SDA
SCL
RSEN
BCLIF
S
SSPIF
Sample SDA when SCL goes high.
If SDA = 0, set BCLIF and release SDA and SCL.
Cleared in software
‘0’
‘0’
FIGURE 9-30: BUS COLLISION DURING REPEATED START CONDITION (CASE 2)
SDA
SCL
BCLIF
RSEN
S
SSPIF
Interrupt cleared
in software
TBRG TBRG
SCL goes low before SDA,
set BCLIF. Release SDA and SCL.
‘0’

PIC16F87XA
9.4.17.3 Bus Collision During a Stop
Condition
Bus collision occurs during a Stop condition if:
a) After the SDA pin has been deasserted and
allowed to float high, SDA is sampled low after
the BRG has timed out.
b) After the SCL pin is deasserted, SCL is sampled
low before SDA goes high.
The Stop condition begins with SDA asserted low.
When SDA is sampled low, the SCL pin is allowed to
float. When the pin is sampled high (clock arbitration),
the Baud Rate Generator is loaded with SSPADD<6:0>
and counts down to 0. After the BRG times out, SDA is
sampled. If SDA is sampled low, a bus collision has
occurred. This is due to another master attempting to
drive a data ‘0’ (Figure 9-31). If the SCL pin is sampled
low before SDA is allowed to float high, a bus collision
occurs. This is another case of another master
attempting to drive a data ‘0’ (Figure 9-32).
FIGURE 9-31: BUS COLLISION DURING A STOP CONDITION (CASE 1)
SDA
SCL
PEN
BCLIF
P
SSPIF
TBRG TBRG TBRG
SDA asserted low
FIGURE 9-32: BUS COLLISION DURING A STOP CONDITION (CASE 2)
SDA sampled
low after TBRG,
set BCLIF
‘0’
‘0’
SDA
SCL
PEN
BCLIF
P
SSPIF
TBRG TBRG TBRG
Assert SDA SCL goes low before SDA goes high,
set BCLIF
‘0’
‘0’

PIC16F87XA
NOTES:

PIC16F87XA
10.0 ADDRESSABLE UNIVERSAL
SYNCHRONOUS
ASYNCHRONOUS RECEIVER
TRANSMITTER (USART)
The Universal Synchronous Asynchronous Receiver
Transmitter (USART) module is one of the two serial
I/O modules. (USART is also known as a Serial
Communications Interface or SCI.) The USART can be
configured as a full-duplex asynchronous system that
can communicate with peripheral devices, such as
CRT terminals and personal computers, or it can be
configured as a half-duplex synchronous system that
can communicate with peripheral devices, such as A/D
or D/A integrated circuits, serial EEPROMs, etc.
The USART can be configured in the following modes:
• Asynchronous (full-duplex)
• Synchronous – Master (half-duplex)
• Synchronous – Slave (half-duplex)
Bit SPEN (RCSTA<7>) and bits TRISC<7:6> have to be
set in order to configure pins RC6/TX/CK and RC7/RX/DT
as the Universal Synchronous Asynchronous Receiver
Transmitter.
The USART module also has a multi-processor
communication capability using 9-bit address detection.
REGISTER 10-1: TXSTA: TRANSMIT STATUS AND CONTROL REGISTER (ADDRESS 98h)
R/W-0 R/W-0 R/W-0 R/W-0 U-0 R/W-0 R-1 R/W-0
CSRC TX9 TXEN SYNC — BRGH TRMT TX9D
bit 7 bit 0
bit 7 CSRC: Clock Source Select bit
Asynchronous mode:
Don’t care.
Synchronous mode:
1 = Master mode (clock generated internally from BRG)
0 = Slave mode (clock from external source)
bit 6 TX9: 9-bit Transmit Enable bit
1 = Selects 9-bit transmission
0 = Selects 8-bit transmission
bit 5 TXEN: Transmit Enable bit
1 = Transmit enabled
0 = Transmit disabled
Note: SREN/CREN overrides TXEN in Sync mode.
bit 4 SYNC: USART Mode Select bit
1 = Synchronous mode
0 = Asynchronous mode
bit 2 BRGH: High Baud Rate Select bit
Asynchronous mode:
1 = High speed
0 = Low speed
Synchronous mode:
bit 1 TRMT: Transmit Shift Register Status bit
1 = TSR empty
0 = TSR full
bit 0 TX9D: 9th bit of Transmit Data, can be Parity bit
Legend:

PIC16F87XA
REGISTER 10-2: RCSTA: RECEIVE STATUS AND CONTROL REGISTER (ADDRESS 18h)
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R-0 R-0 R-x
SPEN RX9 SREN CREN ADDEN FERR OERR RX9D
bit 7 bit 0
bit 7 SPEN: Serial Port Enable bit
1 = Serial port enabled (configures RC7/RX/DT and RC6/TX/CK pins as serial port pins)
0 = Serial port disabled
bit 6 RX9: 9-bit Receive Enable bit
1 = Selects 9-bit reception
0 = Selects 8-bit reception
bit 5 SREN: Single Receive Enable bit
Asynchronous mode:
Don’t care.
Synchronous mode – Master:
1 = Enables single receive
0 = Disables single receive
This bit is cleared after reception is complete.
Synchronous mode – Slave:
Don’t care.
bit 4 CREN: Continuous Receive Enable bit
Asynchronous mode:
1 = Enables continuous receive
0 = Disables continuous receive
Synchronous mode:
1 = Enables continuous receive until enable bit CREN is cleared (CREN overrides SREN)
0 = Disables continuous receive
bit 3 ADDEN: Address Detect Enable bit
Asynchronous mode 9-bit (RX9 = 1):
1 = Enables address detection, enables interrupt and load of the receive buffer when RSR<8>
is set
0 = Disables address detection, all bytes are received and ninth bit can be used as parity bit
bit 2 FERR: Framing Error bit
1 = Framing error (can be updated by reading RCREG register and receive next valid byte)
0 = No framing error
bit 1 OERR: Overrun Error bit
1 = Overrun error (can be cleared by clearing bit CREN)
0 = No overrun error
bit 0 RX9D: 9th bit of Received Data (can be parity bit but must be calculated by user firmware)
Legend:

PIC16F87XA
10.1 USART Baud Rate Generator
(BRG)
The BRG supports both the Asynchronous and Syn-chronous
modes of the USART. It is a dedicated 8-bit
baud rate generator. The SPBRG register controls the
period of a free running 8-bit timer. In Asynchronous
mode, bit BRGH (TXSTA<2>) also controls the baud
rate. In Synchronous mode, bit BRGH is ignored.
Table 10-1 shows the formula for computation of the
baud rate for different USART modes which only apply
in Master mode (internal clock).
Given the desired baud rate and FOSC, the nearest
integer value for the SPBRG register can be calculated
using the formula in Table 10-1. From this, the error in
baud rate can be determined.
It may be advantageous to use the high baud rate
(BRGH = 1) even for slower baud clocks. This is
because the FOSC/(16 (X + 1)) equation can reduce the
baud rate error in some cases.
Writing a new value to the SPBRG register causes the
BRG timer to be reset (or cleared). This ensures the
BRG does not wait for a timer overflow before
outputting the new baud rate.
10.1.1 SAMPLING
The data on the RC7/RX/DT pin is sampled three times
by a majority detect circuit to determine if a high or a
low level is present at the RX pin.
TABLE 10-1: BAUD RATE FORMULA
SYNC BRGH = 0 (Low Speed) BRGH = 1 (High Speed)
0
1
(Asynchronous) Baud Rate = FOSC/(64 (X + 1))
(Synchronous) Baud Rate = FOSC/(4 (X + 1))
Baud Rate = FOSC/(16 (X + 1))
Legend: X = value in SPBRG (0 to 255)
TABLE 10-2: REGISTERS ASSOCIATED WITH BAUD RATE GENERATOR
N/A
Value on:
POR, BOR
Value on
all other
Resets
98h TXSTA CSRC TX9 TXEN SYNC — BRGH TRMT TX9D 0000 -010 0000 -010
18h RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 0000 000x 0000 000x
99h SPBRG Baud Rate Generator Register 0000 0000 0000 0000
Legend: x = unknown, - = unimplemented, read as ‘0’. Shaded cells are not used by the BRG.

PIC16F87XA
TABLE 10-3: BAUD RATES FOR ASYNCHRONOUS MODE (BRGH = 0)
BAUD
RATE
(K)
FOSC = 20 MHz FOSC = 16 MHz FOSC = 10 MHz
KBAUD
%
ERROR
SPBRG
value
(decimal) KBAUD
%
ERROR
SPBRG
value
(decimal) KBAUD
%
ERROR
SPBRG
value
(decimal)
0.3 - - - - - - - - -
1.2 1.221 1.75 255 1.202 0.17 207 1.202 0.17 129
2.4 2.404 0.17 129 2.404 0.17 103 2.404 0.17 64
9.6 9.766 1.73 31 9.615 0.16 25 9.766 1.73 15
19.2 19.531 1.72 15 19.231 0.16 12 19.531 1.72 7
28.8 31.250 8.51 9 27.778 3.55 8 31.250 8.51 4
33.6 34.722 3.34 8 35.714 6.29 6 31.250 6.99 4
57.6 62.500 8.51 4 62.500 8.51 3 52.083 9.58 2
HIGH 1.221 - 255 0.977 - 255 0.610 - 255
LOW 312.500 - 0 250.000 - 0 156.250 - 0
BAUD
RATE
(K)
FOSC = 4 MHz FOSC = 3.6864 MHz
KBAUD
%
ERROR
SPBRG
value
(decimal) KBAUD
%
ERROR
SPBRG
value
(decimal)
0.3 0.300 0 207 0.3 0 191
1.2 1.202 0.17 51 1.2 0 47
2.4 2.404 0.17 25 2.4 0 23
9.6 8.929 6.99 6 9.6 0 5
19.2 20.833 8.51 2 19.2 0 2
28.8 31.250 8.51 1 28.8 0 1
33.6 - - - - - -
57.6 62.500 8.51 0 57.6 0 0
HIGH 0.244 - 255 0.225 - 255
LOW 62.500 - 0 57.6 - 0
TABLE 10-4: BAUD RATES FOR ASYNCHRONOUS MODE (BRGH = 1)
BAUD
RATE
(K)
FOSC = 20 MHz FOSC = 16 MHz FOSC = 10 MHz
KBAUD
%
ERROR
SPBRG
value
(decimal) KBAUD
%
ERROR
SPBRG
value
(decimal) KBAUD
%
ERROR
SPBRG
value
(decimal)
0.3 - - - - - - - - -
1.2 - - - - - - - - -
2.4 - - - - - - 2.441 1.71 255
9.6 9.615 0.16 129 9.615 0.16 103 9.615 0.16 64
19.2 19.231 0.16 64 19.231 0.16 51 19.531 1.72 31
28.8 29.070 0.94 42 29.412 2.13 33 28.409 1.36 21
33.6 33.784 0.55 36 33.333 0.79 29 32.895 2.10 18
57.6 59.524 3.34 20 58.824 2.13 16 56.818 1.36 10
HIGH 4.883 - 255 3.906 - 255 2.441 - 255
LOW 1250.000 - 0 1000.000 0 625.000 - 0
BAUD
RATE
(K)
FOSC = 4 MHz FOSC = 3.6864 MHz
KBAUD
%
ERROR
SPBRG
value
(decimal) KBAUD
%
ERROR
SPBRG
value
(decimal)
0.3 - - - - - -
1.2 1.202 0.17 207 1.2 0 191
2.4 2.404 0.17 103 2.4 0 95
9.6 9.615 0.16 25 9.6 0 23
19.2 19.231 0.16 12 19.2 0 11
28.8 27.798 3.55 8 28.8 0 7
33.6 35.714 6.29 6 32.9 2.04 6
57.6 62.500 8.51 3 57.6 0 3
HIGH 0.977 - 255 0.9 - 255
LOW 250.000 - 0 230.4 - 0

PIC16F87XA
10.2 USART Asynchronous Mode
In this mode, the USART uses standard Non-Return-to-
Zero (NRZ) format (one Start bit, eight or nine data
bits and one Stop bit). The most common data format
is 8 bits. An on-chip, dedicated, 8-bit Baud Rate
Generator can be used to derive standard baud rate
frequencies from the oscillator. The USART transmits
and receives the LSb first. The transmitter and receiver
are functionally independent but use the same data
format and baud rate. The baud rate generator
produces a clock, either x16 or x64 of the bit shift rate,
depending on bit BRGH (TXSTA<2>). Parity is not
supported by the hardware but can be implemented in
software (and stored as the ninth data bit).
Asynchronous mode is stopped during Sleep.
Asynchronous mode is selected by clearing bit SYNC
(TXSTA<4>).
The USART Asynchronous module consists of the
following important elements:
• Baud Rate Generator
• Sampling Circuit
• Asynchronous Transmitter
• Asynchronous Receiver
10.2.1 USART ASYNCHRONOUS
TRANSMITTER
The USART transmitter block diagram is shown in
Figure 10-1. The heart of the transmitter is the Transmit
(Serial) Shift Register (TSR). The shift register obtains
its data from the Read/Write Transmit Buffer, TXREG.
The TXREG register is loaded with data in software.
The TSR register is not loaded until the Stop bit has
been transmitted from the previous load. As soon as
the Stop bit is transmitted, the TSR is loaded with new
data from the TXREG register (if available). Once the
TXREG register transfers the data to the TSR register
(occurs in one TCY), the TXREG register is empty and
flag bit, TXIF (PIR1<4>), is set. This interrupt can be
enabled/disabled by setting/clearing enable bit, TXIE
(PIE1<4>). Flag bit TXIF will be set regardless of the
state of enable bit TXIE and cannot be cleared in soft-ware.
It will reset only when new data is loaded into the
TXREG register. While flag bit TXIF indicates the status
of the TXREG register, another bit, TRMT (TXSTA<1>),
shows the status of the TSR register. Status bit TRMT
is a read-only bit which is set when the TSR register is
empty. No interrupt logic is tied to this bit so the user
has to poll this bit in order to determine if the TSR
register is empty.
Note 1: The TSR register is not mapped in data
memory so it is not available to the user.
2: Flag bit TXIF is set when enable bit TXEN
is set. TXIF is cleared by loading TXREG.
Transmission is enabled by setting enable bit, TXEN
(TXSTA<5>). The actual transmission will not occur
until the TXREG register has been loaded with data
and the Baud Rate Generator (BRG) has produced a
shift clock (Figure 10-2). The transmission can also be
started by first loading the TXREG register and then
setting enable bit TXEN. Normally, when transmission
is first started, the TSR register is empty. At that point,
transfer to the TXREG register will result in an immedi-ate
transfer to TSR, resulting in an empty TXREG. A
back-to-back transfer is thus possible (Figure 10-3).
Clearing enable bit TXEN during a transmission will
cause the transmission to be aborted and will reset the
transmitter. As a result, the RC6/TX/CK pin will revert
to high-impedance.
In order to select 9-bit transmission, transmit bit TX9
(TXSTA<6>) should be set and the ninth bit should be
written to TX9D (TXSTA<0>). The ninth bit must be
written before writing the 8-bit data to the TXREG reg-ister.
This is because a data write to the TXREG regis-ter
can result in an immediate transfer of the data to the
TSR register (if the TSR is empty). In such a case, an
incorrect ninth data bit may be loaded in the TSR
register.
FIGURE 10-1: USART TRANSMIT BLOCK DIAGRAM
TXIF
TXIE
Interrupt
Data Bus
TXREG Register
8
MSb LSb
(8) 0
TXEN Baud Rate CLK
SPBRG
Baud Rate Generator
• • •
TSR Register
TX9
TX9D
Pin Buffer
and Control
TRMT SPEN
RC6/TX/CK pin

PIC16F87XA
When setting up an Asynchronous Transmission,
follow these steps:
1. Initialize the SPBRG register for the appropriate
baud rate. If a high-speed baud rate is desired,
set bit BRGH (Section 10.1 “USART Baud
Rate Generator (BRG)”).
2. Enable the asynchronous serial port by clearing
bit SYNC and setting bit SPEN.
3. If interrupts are desired, then set enable bit TXIE.
4. If 9-bit transmission is desired, then set transmit
bit TX9.
5. Enable the transmission by setting bit TXEN,
which will also set bit TXIF.
6. If 9-bit transmission is selected, the ninth bit
should be loaded in bit TX9D.
7. Load data to the TXREG register (starts
transmission).
8. If using interrupts, ensure that GIE and PEIE
(bits 7 and 6) of the INTCON register are set.
FIGURE 10-2: ASYNCHRONOUS MASTER TRANSMISSION
Start Bit Bit 0 Bit 1 Bit 7/8
Word 1
Stop Bit
Word 1
Word 1
Transmit Shift Reg
Write to TXREG
BRG Output
(Shift Clock)
RC6/TX/CK (pin)
TXIF bit
(Transmit Buffer
Reg. Empty Flag)
TRMT bit
(Transmit Shift
Reg. Empty Flag)
FIGURE 10-3: ASYNCHRONOUS MASTER TRANSMISSION (BACK TO BACK)
Word 1 Word 2
Start Bit Stop Bit Start Bit
Bit 0 Bit 1 Bit 7/8 Bit 0
Word 1 Word 2
Word 1 Word 2
Transmit Shift Reg.
Write to TXREG
BRG Output
(Shift Clock)
RC6/TX/CK (pin)
TXIF bit
(Interrupt Reg. Flag)
TRMT bit
(Transmit Shift
Reg. Empty Flag)
Transmit Shift Reg.
Note: This timing diagram shows two consecutive transmissions.
TABLE 10-5: REGISTERS ASSOCIATED WITH ASYNCHRONOUS TRANSMISSION
Value on:
POR, BOR
Value on
all other
Resets
0Bh, 8Bh,
10Bh,18Bh
INTCON GIE PEIE TMR0IE INTE RBIE TMR0IF INTF R0IF 0000 000x 0000 000u
18h RCSTA SPEN RX9 SREN CREN — FERR OERR RX9D 0000 -00x 0000 -00x
19h TXREG USART Transmit Register 0000 0000 0000 0000
Legend: x = unknown, - = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous transmission.

PIC16F87XA
10.2.2 USART ASYNCHRONOUS
RECEIVER
The receiver block diagram is shown in Figure 10-4.
The data is received on the RC7/RX/DT pin and drives
the data recovery block. The data recovery block is
actually a high-speed shifter, operating at x16 times the
baud rate; whereas the main receive serial shifter
operates at the bit rate or at FOSC.
Once Asynchronous mode is selected, reception is
enabled by setting bit CREN (RCSTA<4>).
The heart of the receiver is the Receive (Serial) Shift
Register (RSR). After sampling the Stop bit, the
received data in the RSR is transferred to the RCREG
register (if it is empty). If the transfer is complete, flag
bit, RCIF (PIR1<5>), is set. The actual interrupt can be
enabled/disabled by setting/clearing enable bit, RCIE
(PIE1<5>). Flag bit RCIF is a read-only bit which is
cleared by the hardware. It is cleared when the RCREG
register has been read and is empty. The RCREG is a
double-buffered register (i.e., it is a two-deep FIFO). It
is possible for two bytes of data to be received and
transferred to the RCREG FIFO and a third byte to
begin shifting to the RSR register. On the detection of
the Stop bit of the third byte, if the RCREG register is
still full, the Overrun Error bit, OERR (RCSTA<1>), will
be set. The word in the RSR will be lost. The RCREG
register can be read twice to retrieve the two bytes in
the FIFO. Overrun bit OERR has to be cleared in soft-ware.
This is done by resetting the receive logic (CREN
is cleared and then set). If bit OERR is set, transfers
from the RSR register to the RCREG register are inhib-ited
and no further data will be received. It is, therefore,
essential to clear error bit OERR if it is set. Framing
error bit, FERR (RCSTA<2>), is set if a Stop bit is
detected as clear. Bit FERR and the 9th receive bit are
buffered the same way as the receive data. Reading
the RCREG will load bits RX9D and FERR with new
values, therefore, it is essential for the user to read the
RCSTA register before reading the RCREG register in
order not to lose the old FERR and RX9D information.
FIGURE 10-4: USART RECEIVE BLOCK DIAGRAM
x64 Baud Rate CLK
SPBRG
Baud Rate Generator
FOSC
RC7/RX/DT
Pin Buffer
and Control
SPEN
CREN
÷64
or
÷16
Data
Recovery
OERR FERR
MSb RSR Register LSb
Stop (8) 7 1 0 Start
• • •
RX9D RCREG Register
FIFO
RX9
Interrupt RCIF
RCIE
Data Bus
8

PIC16F87XA
FIGURE 10-5: ASYNCHRONOUS RECEPTION
Start
bit bit 0 bit 1 bit 7/8 Stop bit 0 bit 7/8
bit
RX (pin)
Rcv Shift
Reg
Rcv Buffer Reg
Read Rcv
Buffer Reg
RCREG
RCIF
(Interrupt Flag)
OERR bit
CREN
Note: This timing diagram shows three words appearing on the RX input. The RCREG (Receive Buffer) is read after the third word,
causing the OERR (Overrun Error) bit to be set.
When setting up an Asynchronous Reception, follow
these steps:
set bit BRGH (Section 10.1 “USART Baud
Rate Generator (BRG)”).
2. Enable the asynchronous serial port by clearing
3. If interrupts are desired, then set enable bit
RCIE.
4. If 9-bit reception is desired, then set bit RX9.
5. Enable the reception by setting bit CREN.
Start
bit 7/8 Stop bit
bit
Word 2
RCREG
Stop
bit
6. Flag bit RCIF will be set when reception is com-plete
and an interrupt will be generated if enable
bit RCIE is set.
7. Read the RCSTA register to get the ninth bit (if
enabled) and determine if any error occurred
during reception.
8. Read the 8-bit received data by reading the
RCREG register.
9. If any error occurred, clear the error by clearing
enable bit CREN.
Start
bit
Word 1
RCREG
TABLE 10-6: REGISTERS ASSOCIATED WITH ASYNCHRONOUS RECEPTION
Value on:
POR, BOR
Value on
all other
Resets
0Bh, 8Bh,
10Bh,18Bh
1Ah RCREG USART Receive Register 0000 0000 0000 0000
Legend: x = unknown, - = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous reception.

PIC16F87XA
10.2.3 SETTING UP 9-BIT MODE WITH
ADDRESS DETECT
When setting up an Asynchronous Reception with
address detect enabled:
• Initialize the SPBRG register for the appropriate
set bit BRGH.
• Enable the asynchronous serial port by clearing
• If interrupts are desired, then set enable bit RCIE.
• Set bit RX9 to enable 9-bit reception.
• Set ADDEN to enable address detect.
• Enable the reception by setting enable bit CREN.
• Flag bit RCIF will be set when reception is
complete, and an interrupt will be generated if
enable bit RCIE was set.
• Read the RCSTA register to get the ninth bit and
determine if any error occurred during reception.
• Read the 8-bit received data by reading the
RCREG register to determine if the device is
being addressed.
• If any error occurred, clear the error by clearing
enable bit CREN.
• If the device has been addressed, clear the
ADDEN bit to allow data bytes and address bytes
to be read into the receive buffer and interrupt the
CPU.
FIGURE 10-6: USART RECEIVE BLOCK DIAGRAM
x64 Baud Rate CLK
SPBRG
Baud Rate Generator
FOSC
RC7/RX/DT
Pin Buffer
and Control
SPEN
CREN
÷ 64
or
÷ 16
Data
Recovery
OERR FERR
MSb RSR Register LSb
• • •
Stop (8) 7 1 0 Start
8
8
RX9D RCREG Register
FIFO
RX9
Enable
Load of
Receive
Buffer
Interrupt RCIF
RCIE
Data Bus
8
RX9
ADDEN
RX9
ADDEN
RSR<8>

PIC16F87XA
FIGURE 10-7: ASYNCHRONOUS RECEPTION WITH ADDRESS DETECT
Start
bit bit 0 bit 1 bit 8 Stop bit 0
bit
Start
bit bit 8 Stop
bit
RC7/RX/DT
(pin)
Load RSR
Read
RCIF
Word 1
RCREG
Bit 8 = 0, Data Byte Bit 8 = 1, Address Byte
Note: This timing diagram shows a data byte followed by an address byte. The data byte is not read into the RCREG (Receive Buffer)
because ADDEN = 1.
FIGURE 10-8: ASYNCHRONOUS RECEPTION WITH ADDRESS BYTE FIRST
Start
bit bit 0 bit 1 bit 8 Stop bit 0
bit
Start
bit bit 8 Stop
bit
RC7/RX/DT
(pin)
Load RSR
Read
RCIF
Word 1
RCREG
Bit 8 = 1, Address Byte Bit 8 = 0, Data Byte
Note: This timing diagram shows a data byte followed by an address byte. The data byte is not read into the RCREG (Receive Buffer)
because ADDEN was not updated and still = 0.
TABLE 10-7: REGISTERS ASSOCIATED WITH ASYNCHRONOUS RECEPTION
Value on:
POR, BOR
Value on
all other
Resets
0Bh, 8Bh,
10Bh,18Bh
Legend: x = unknown, - = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous reception.

PIC16F87XA
10.3 USART Synchronous
Master Mode
In Synchronous Master mode, the data is transmitted in
a half-duplex manner (i.e., transmission and reception
do not occur at the same time). When transmitting data,
the reception is inhibited and vice versa. Synchronous
mode is entered by setting bit, SYNC (TXSTA<4>). In
addition, enable bit, SPEN (RCSTA<7>), is set in order
to configure the RC6/TX/CK and RC7/RX/DT I/O pins
to CK (clock) and DT (data) lines, respectively. The
Master mode indicates that the processor transmits the
master clock on the CK line. The Master mode is
entered by setting bit, CSRC (TXSTA<7>).
10.3.1 USART SYNCHRONOUS MASTER
TRANSMISSION
The USART transmitter block diagram is shown in
Figure 10-6. The heart of the transmitter is the Transmit
(Serial) Shift Register (TSR). The shift register obtains
its data from the Read/Write Transmit Buffer register,
TXREG. The TXREG register is loaded with data in
software. The TSR register is not loaded until the last
bit has been transmitted from the previous load. As
soon as the last bit is transmitted, the TSR is loaded
with new data from the TXREG (if available). Once the
TXREG register transfers the data to the TSR register
(occurs in one TCYCLE), the TXREG is empty and inter-rupt
bit, TXIF (PIR1<4>), is set. The interrupt can be
enabled/disabled by setting/clearing enable bit TXIE
(PIE1<4>). Flag bit TXIF will be set regardless of the
state of enable bit TXIE and cannot be cleared in soft-ware.
It will reset only when new data is loaded into the
TXREG register. While flag bit TXIF indicates the status
of the TXREG register, another bit, TRMT (TXSTA<1>),
shows the status of the TSR register. TRMT is a read-only
bit which is set when the TSR is empty. No inter-rupt
logic is tied to this bit so the user has to poll this bit
in order to determine if the TSR register is empty. The
TSR is not mapped in data memory so it is not available
to the user.
Transmission is enabled by setting enable bit, TXEN
(TXSTA<5>). The actual transmission will not occur
until the TXREG register has been loaded with data.
The first data bit will be shifted out on the next available
rising edge of the clock on the CK line. Data out is
stable around the falling edge of the synchronous clock
(Figure 10-9). The transmission can also be started by
first loading the TXREG register and then setting bit
TXEN (Figure 10-10). This is advantageous when slow
baud rates are selected since the BRG is kept in Reset
when bits TXEN, CREN and SREN are clear. Setting
enable bit TXEN will start the BRG, creating a shift
clock immediately. Normally, when transmission is first
started, the TSR register is empty so a transfer to the
TXREG register will result in an immediate transfer to
TSR, resulting in an empty TXREG. Back-to-back
transfers are possible.
Clearing enable bit TXEN during a transmission will
cause the transmission to be aborted and will reset the
transmitter. The DT and CK pins will revert to high-impedance.
If either bit CREN or bit SREN is set during
a transmission, the transmission is aborted and the DT
pin reverts to a high-impedance state (for a reception).
The CK pin will remain an output if bit CSRC is set
(internal clock). The transmitter logic, however, is not
reset, although it is disconnected from the pins. In order
to reset the transmitter, the user has to clear bit TXEN.
If bit SREN is set (to interrupt an on-going transmission
and receive a single word), then after the single word is
received, bit SREN will be cleared and the serial port
will revert back to transmitting since bit TXEN is still set.
The DT line will immediately switch from High-
Impedance Receive mode to transmit and start driving.
To avoid this, bit TXEN should be cleared.
In order to select 9-bit transmission, the TX9
(TXSTA<6>) bit should be set and the ninth bit should
be written to bit TX9D (TXSTA<0>). The ninth bit must
be written before writing the 8-bit data to the TXREG
register. This is because a data write to the TXREG can
result in an immediate transfer of the data to the TSR
register (if the TSR is empty). If the TSR was empty and
the TXREG was written before writing the “new” TX9D,
the “present” value of bit TX9D is loaded.
Steps to follow when setting up a Synchronous Master
Transmission:
baud rate (Section 10.1 “USART Baud Rate
Generator (BRG)”).
2. Enable the synchronous master serial port by
setting bits SYNC, SPEN and CSRC.
3. If interrupts are desired, set enable bit TXIE.
4. If 9-bit transmission is desired, set bit TX9.
5. Enable the transmission by setting bit TXEN.
7. Start transmission by loading data to the TXREG
register.

PIC16F87XA
TABLE 10-8: REGISTERS ASSOCIATED WITH SYNCHRONOUS MASTER TRANSMISSION
0Bh, 8Bh,
10Bh,18Bh
Legend: x = unknown, - = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master transmission.
FIGURE 10-9: SYNCHRONOUS TRANSMISSION
Q1Q2 Q3 Q4 Q1Q2 Q3 Q4Q1Q2Q3 Q4Q1Q2Q3 Q4Q1 Q2 Q3 Q4 Q3 Q4 Q1Q2 Q3Q4 Q1Q2Q3Q4 Q1Q2Q3 Q4Q1 Q2Q3Q4 Q1Q2Q3 Q4Q1Q2Q3 Q4
RC7/RX/DT bit 0 bit 1 bit 2 bit 7
bit 0 bit 1 bit 7
Word 1
pin
RC6/TX/CK
pin
Write to
TXREG reg
TXIF bit
(Interrupt Flag)
TRMT bit
TXEN bit
Word 2
Write Word 1 Write Word 2
‘1’ ‘1’
Note: Sync Master mode; SPBRG = 0. Continuous transmission of two 8-bit words.
FIGURE 10-10: SYNCHRONOUS TRANSMISSION (THROUGH TXEN)
Value on:
POR, BOR
Value on
all other
Resets
RC7/RX/DT pin
RC6/TX/CK pin
Write to
TXREG Reg
TXIF bit
TRMT bit
bit 0 bit 1 bit 2 bit 6 bit 7
TXEN bit

PIC16F87XA
10.3.2 USART SYNCHRONOUS MASTER
RECEPTION
Once Synchronous mode is selected, reception is
enabled by setting either enable bit, SREN
(RCSTA<5>), or enable bit, CREN (RCSTA<4>). Data
is sampled on the RC7/RX/DT pin on the falling edge of
the clock. If enable bit SREN is set, then only a single
word is received. If enable bit CREN is set, the recep-tion
is continuous until CREN is cleared. If both bits are
set, CREN takes precedence. After clocking the last bit,
the received data in the Receive Shift Register (RSR)
is transferred to the RCREG register (if it is empty).
When the transfer is complete, interrupt flag bit, RCIF
(PIR1<5>), is set. The actual interrupt can be enabled/
disabled by setting/clearing enable bit, RCIE
(PIE1<5>). Flag bit RCIF is a read-only bit which is
reset by the hardware. In this case, it is reset when the
RCREG register has been read and is empty. The
RCREG is a double-buffered register (i.e., it is a two-deep
FIFO). It is possible for two bytes of data to be
received and transferred to the RCREG FIFO and a
third byte to begin shifting into the RSR register. On the
clocking of the last bit of the third byte, if the RCREG
register is still full, then Overrun Error bit, OERR
(RCSTA<1>), is set. The word in the RSR will be lost.
The RCREG register can be read twice to retrieve the
two bytes in the FIFO. Bit OERR has to be cleared in
software (by clearing bit CREN). If bit OERR is set,
transfers from the RSR to the RCREG are inhibited so
it is essential to clear bit OERR if it is set. The ninth
receive bit is buffered the same way as the receive
data. Reading the RCREG register will load bit RX9D
with a new value, therefore, it is essential for the user
to read the RCSTA register before reading RCREG in
order not to lose the old RX9D information.
When setting up a Synchronous Master Reception:
baud rate (Section 10.1 “USART Baud Rate
Generator (BRG)”).
setting bits SYNC, SPEN and CSRC.
3. Ensure bits CREN and SREN are clear.
RCIE.
5. If 9-bit reception is desired, then set bit RX9.
6. If a single reception is required, set bit SREN.
For continuous reception, set bit CREN.
7. Interrupt flag bit RCIF will be set when reception
is complete and an interrupt will be generated if
during reception.
RCREG register.
bit CREN.
TABLE 10-9: REGISTERS ASSOCIATED WITH SYNCHRONOUS MASTER RECEPTION
Value on:
POR, BOR
Value on
all other
Resets
0Bh, 8Bh,
10Bh,18Bh
Legend: x = unknown, - = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master reception.

PIC16F87XA
FIGURE 10-11: SYNCHRONOUS RECEPTION (MASTER MODE, SREN)
Q2Q3Q4Q1Q2Q3Q4Q1Q2Q3Q4 Q1Q2Q3Q4Q1Q2Q3Q4 Q1Q2Q3Q4Q1Q2Q3Q4 Q1Q2Q3Q4Q1Q2Q3Q4 Q1Q2Q3Q4
RC7/RX/DT
pin
RC6/TX/CK
pin
Write to
bit SREN
SREN bit
CREN bit
RCIF bit
(Interrupt)
Read
RXREG
‘0’
Note: Timing diagram demonstrates Sync Master mode with bit SREN = 1 and bit BRG = 0.
10.4 USART Synchronous Slave Mode
Synchronous Slave mode differs from the Master mode
in the fact that the shift clock is supplied externally at
the RC6/TX/CK pin (instead of being supplied internally
in Master mode). This allows the device to transfer or
receive data while in Sleep mode. Slave mode is
entered by clearing bit, CSRC (TXSTA<7>).
10.4.1 USART SYNCHRONOUS SLAVE
TRANSMIT
The operation of the Synchronous Master and Slave
modes is identical, except in the case of the Sleep mode.
If two words are written to the TXREG and then the
SLEEP instruction is executed, the following will occur:
a) The first word will immediately transfer to the
TSR register and transmit.
b) The second word will remain in TXREG register.
c) Flag bit TXIF will not be set.
d) When the first word has been shifted out of TSR,
the TXREG register will transfer the second word
to the TSR and flag bit TXIF will now be set.
e) If enable bit TXIE is set, the interrupt will wake
the chip from Sleep and if the global interrupt is
enabled, the program will branch to the interrupt
vector (0004h).
Q1 Q2Q3Q4
‘0’
When setting up a Synchronous Slave Transmission,
follow these steps:
1. Enable the synchronous slave serial port by set-ting
bits SYNC and SPEN and clearing bit
CSRC.
2. Clear bits CREN and SREN.
TXIE.
4. If 9-bit transmission is desired, then set bit TX9.
5. Enable the transmission by setting enable bit
TXEN.
7. Start transmission by loading data to the TXREG
register.

PIC16F87XA
TABLE 10-10: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE TRANSMISSION
0Bh, 8Bh,
10Bh,18Bh
Legend: x = unknown, - = unimplemented, read as ‘0’. Shaded cells are not used for synchronous slave transmission.
10.4.2 USART SYNCHRONOUS SLAVE
RECEPTION
The operation of the Synchronous Master and Slave
modes is identical, except in the case of the Sleep
mode. Bit SREN is a “don't care” in Slave mode.
If receive is enabled by setting bit CREN prior to the
SLEEP instruction, then a word may be received during
Sleep. On completely receiving the word, the RSR reg-ister
will transfer the data to the RCREG register and if
enable bit RCIE bit is set, the interrupt generated will
wake the chip from Sleep. If the global interrupt is
enabled, the program will branch to the interrupt vector
(0004h).
Value on:
POR, BOR
Value on
all other
Resets
When setting up a Synchronous Slave Reception,
follow these steps:
setting bits SYNC and SPEN and clearing bit
CSRC.
2. If interrupts are desired, set enable bit RCIE.
3. If 9-bit reception is desired, set bit RX9.
4. To enable reception, set enable bit CREN.
5. Flag bit RCIF will be set when reception is
complete and an interrupt will be generated if
during reception.
RCREG register.
bit CREN.
TABLE 10-11: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE RECEPTION
Value on:
POR, BOR
Value on
all other
Resets
0Bh, 8Bh,
10Bh,18Bh
Legend: x = unknown, - = unimplemented, read as ‘0’. Shaded cells are not used for synchronous slave reception.
Note 1: Bits PSPIE and PSPIF are reserved on 28-pin devices, always maintain these bits clear.

PIC16F87XA
NOTES:

PIC16F87XA
11.0 ANALOG-TO-DIGITAL
CONVERTER (A/D) MODULE
The Analog-to-Digital (A/D) Converter module has five
inputs for the 28-pin devices and eight for the 40/44-pin
devices.
The conversion of an analog input signal results in a
corresponding 10-bit digital number. The A/D module
has high and low-voltage reference input that is soft-ware
selectable to some combination of VDD, VSS, RA2
or RA3.
The A/D converter has a unique feature of being able
to operate while the device is in Sleep mode. To
operate in Sleep, the A/D clock must be derived from
the A/D’s internal RC oscillator.
The A/D module has four registers. These registers are:
• A/D Result High Register (ADRESH)
• A/D Result Low Register (ADRESL)
• A/D Control Register 0 (ADCON0)
• A/D Control Register 1 (ADCON1)
The ADCON0 register, shown in Register 11-1, con-trols
the operation of the A/D module. The ADCON1
register, shown in Register 11-2, configures the func-tions
of the port pins. The port pins can be configured
as analog inputs (RA3 can also be the voltage
reference) or as digital I/O.
Additional information on using the A/D module can be
found in the PICmicro® Mid-Range MCU Family
Reference Manual (DS33023).
REGISTER 11-1: ADCON0 REGISTER (ADDRESS 1Fh)
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 U-0 R/W-0
ADCS1 ADCS0 CHS2 CHS1 CHS0 GO/DONE — ADON
bit 7 bit 0
bit 7-6 ADCS1:ADCS0: A/D Conversion Clock Select bits (ADCON0 bits in bold)
ADCON1
<ADCS2>
ADCON0
<ADCS1:ADCS0> Clock Conversion
0 00 FOSC/2
0 01 FOSC/8
0 10 FOSC/32
0 11 FRC (clock derived from the internal A/D RC oscillator)
1 00 FOSC/4
1 01 FOSC/16
1 10 FOSC/64
bit 5-3 CHS2:CHS0: Analog Channel Select bits
000 = Channel 0 (AN0)
Note: The PIC16F873A/876A devices only implement A/D channels 0 through 4; the
unimplemented selections are reserved. Do not select any unimplemented
channels with these devices.
bit 2 GO/DONE: A/D Conversion Status bit
When ADON = 1:
1 = A/D conversion in progress (setting this bit starts the A/D conversion which is automatically
cleared by hardware when the A/D conversion is complete)
0 = A/D conversion not in progress
bit 0 ADON: A/D On bit
1 = A/D converter module is powered up
0 = A/D converter module is shut-off and consumes no operating current
Legend:

PIC16F87XA
REGISTER 11-2: ADCON1 REGISTER (ADDRESS 9Fh)
R/W-0 R/W-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0
ADFM ADCS2 — — PCFG3 PCFG2 PCFG1 PCFG0
bit 7 bit 0
bit 7 ADFM: A/D Result Format Select bit
1 = Right justified. Six (6) Most Significant bits of ADRESH are read as ‘0’.
0 = Left justified. Six (6) Least Significant bits of ADRESL are read as ‘0’.
bit 6 ADCS2: A/D Conversion Clock Select bit (ADCON1 bits in shaded area and in bold)
ADCON1
<ADCS2>
ADCON0
<ADCS1:ADCS0>
0 00 FOSC/2
0 01 FOSC/8
0 10 FOSC/32
1 00 FOSC/4
1 01 FOSC/16
1 10 FOSC/64
bit 3-0 PCFG3:PCFG0: A/D Port Configuration Control bits
Clock Conversion
PCFG
<3:0>
AN7 AN6 AN5 AN4 AN3 AN2 AN1 AN0 VREF+ VREF- C/R
0000 A A A A A A A A VDD VSS 8/0
0001 A A A A VREF+ A A A AN3 VSS 7/1
0010 D D D A A A A A VDD VSS 5/0
0011 D D D A VREF+ A A A AN3 VSS 4/1
0100 D D D D A D A A VDD VSS 3/0
0101 D D D D VREF+ D A A AN3 VSS 2/1
011x D D D D D D D D — — 0/0
1000 A A A A VREF+ VREF- A A AN3 AN2 6/2
1001 D D A A A A A A VDD VSS 6/0
1010 D D A A VREF+ A A A AN3 VSS 5/1
1011 D D A A VREF+ VREF- A A AN3 AN2 4/2
1100 D D D A VREF+ VREF- A A AN3 AN2 3/2
1101 D D D D VREF+ VREF- A A AN3 AN2 2/2
1110 D D D D D D D A VDD VSS 1/0
1111 D D D D VREF+ VREF- D A AN3 AN2 1/2
A = Analog input D = Digital I/O
C/R = # of analog input channels/# of A/D voltage references
Legend:
Note: On any device Reset, the port pins that are multiplexed with analog functions (ANx)
are forced to be an analog input.

PIC16F87XA
The ADRESH:ADRESL registers contain the 10-bit
result of the A/D conversion. When the A/D conversion
is complete, the result is loaded into this A/D Result
register pair, the GO/DONE bit (ADCON0<2>) is cleared
and the A/D interrupt flag bit ADIF is set. The block
diagram of the A/D module is shown in Figure 11-1.
After the A/D module has been configured as desired,
the selected channel must be acquired before the con-version
is started. The analog input channels must
have their corresponding TRIS bits selected as inputs.
To determine sample time, see Section 11.1 “A/D
Acquisition Requirements”. After this acquisition
time has elapsed, the A/D conversion can be started.
To do an A/D Conversion, follow these steps:
1. Configure the A/D module:
• Configure analog pins/voltage reference and
digital I/O (ADCON1)
• Select A/D input channel (ADCON0)
• Select A/D conversion clock (ADCON0)
• Turn on A/D module (ADCON0)
2. Configure A/D interrupt (if desired):
• Clear ADIF bit
• Set ADIE bit
• Set PEIE bit
• Set GIE bit
3. Wait the required acquisition time.
4. Start conversion:
• Set GO/DONE bit (ADCON0)
5. Wait for A/D conversion to complete by either:
• Polling for the GO/DONE bit to be cleared
(interrupts disabled); OR
• Waiting for the A/D interrupt
6. Read A/D Result register pair
(ADRESH:ADRESL), clear bit ADIF if required.
7. For the next conversion, go to step 1 or step 2
as required. The A/D conversion time per bit is
defined as TAD.
FIGURE 11-1: A/D BLOCK DIAGRAM
VAIN
(Input Voltage)
VREF+
(Reference
Voltage)
VDD
PCFG3:PCFG0
CHS2:CHS0
RE2/AN7(1)
RE1/AN6(1)
RE0/AN5(1)
RA5/AN4
RA3/AN3/VREF+
RA2/AN2/VREF-RA1/
AN1
RA0/AN0
111
110
101
100
011
010
001
000
A/D
Converter
VREF-
(Reference
Voltage)
Note 1: Not available on 28-pin devices.
VSS
PCFG3:PCFG0

PIC16F87XA
11.1 A/D Acquisition Requirements
For the A/D converter to meet its specified accuracy,
the charge holding capacitor (CHOLD) must be allowed
to fully charge to the input channel voltage level. The
analog input model is shown in Figure 11-2. The source
impedance (RS) and the internal sampling switch
impedance (RSS) directly affect the time required to
charge the capacitor CHOLD. The sampling switch
(RSS) impedance varies over the device voltage (VDD);
see Figure 11-2. The maximum recommended
impedance for analog sources is 2.5 kΩ. As the
impedance is decreased, the acquisition time may be
decreased. After the analog input channel is selected
(changed), this acquisition must be done before the
conversion can be started.
To calculate the minimum acquisition time,
Equation 11-1 may be used. This equation assumes
that 1/2 LSb error is used (1024 steps for the A/D). The
1/2 LSb error is the maximum error allowed for the A/D
to meet its specified resolution.
To calculate the minimum acquisition time, TACQ, see
Manual (DS33023).
EQUATION 11-1: ACQUISITION TIME
TACQ
TC
TACQ
=
=
=
=
=
=
=
=
Amplifier Settling Time + Hold Capacitor Charging Time + Temperature Coefficient
TAMP + TC + TCOFF
2 μs + TC + [(Temperature – 25°C)(0.05 μs/°C)]
CHOLD (RIC + RSS + RS) In(1/2047)
- 120 pF (1 kΩ + 7 kΩ + 10 kΩ) In(0.0004885)
16.47 μs
2 μs + 16.47 μs + [(50°C – 25°C)(0.05 μs/°C)
19.72 μs
Note 1: The reference voltage (VREF) has no effect on the equation since it cancels itself out.
2: The charge holding capacitor (CHOLD) is not discharged after each conversion.
3: The maximum recommended impedance for analog sources is 2.5 kΩ. This is required to meet the pin
leakage specification.
FIGURE 11-2: ANALOG INPUT MODEL
RS ANx
VA CPIN
5 pF
Sampling
Switch
SS RSS
± 500 nA = 120 pF
VDD
VDD
VT = 0.6V
RIC ≤ 1K
VT = 0.6V ILEAKAGE
CHOLD
= DAC Capacitance
VSS
6V
5 6 7 8 91011
Sampling Switch
5V
4V
3V
2V
(kΩ)
Legend: CPIN
VT
ILEAKAGE
RIC
SS
CHOLD
= input capacitance
= threshold voltage
= leakage current at the pin due to
various junctions
= interconnect resistance
= sampling switch
= sample/hold capacitance (from DAC)

PIC16F87XA
11.2 Selecting the A/D Conversion
Clock
The A/D conversion time per bit is defined as TAD. The
A/D conversion requires a minimum 12 TAD per 10-bit
conversion. The source of the A/D conversion clock is
software selected. The seven possible options for TAD
are:
• 2 TOSC
• 4 TOSC
• 8 TOSC
• 16 TOSC
• 32 TOSC
• 64 TOSC
• Internal A/D module RC oscillator (2-6 μs)
For correct A/D conversions, the A/D conversion clock
(TAD) must be selected to ensure a minimum TAD time
of 1.6 μs.
Table 11-1 shows the resultant TAD times derived from
the device operating frequencies and the A/D clock
source selected.
11.3 Configuring Analog Port Pins
The ADCON1 and TRIS registers control the operation
of the A/D port pins. The port pins that are desired as
analog inputs must have their corresponding TRIS bits
set (input). If the TRIS bit is cleared (output), the digital
output level (VOH or VOL) will be converted.
The A/D operation is independent of the state of the
CHS2:CHS0 bits and the TRIS bits.
Note 1: When reading the port register, any pin
configured as an analog input channel will
read as cleared (a low level). Pins config-ured
as digital inputs will convert an analog
input. Analog levels on a digitally config-ured
input will not affect the conversion
accuracy.
2: Analog levels on any pin that is defined as
a digital input (including the AN7:AN0
pins) may cause the input buffer to con-sume
current that is out of the device
specifications.
TABLE 11-1: TAD vs. MAXIMUM DEVICE OPERATING FREQUENCIES (STANDARD DEVICES (F))
AD Clock Source (TAD)
Maximum Device Frequency
Operation ADCS2:ADCS1:ADCS0
2 TOSC 000 1.25 MHz
4 TOSC 100 2.5 MHz
8 TOSC 001 5 MHz
16 TOSC 101 10 MHz
32 TOSC 010 20 MHz
64 TOSC 110 20 MHz
RC(1, 2, 3) x11 (Note 1)
Note 1: The RC source has a typical TAD time of 4 μs but can vary between 2-6 μs.
2: When the device frequencies are greater than 1 MHz, the RC A/D conversion clock source is only
recommended for Sleep operation.
3: For extended voltage devices (LF), please refer to Section 17.0 “Electrical Characteristics”.

PIC16F87XA
11.4 A/D Conversions
Clearing the GO/DONE bit during a conversion will
abort the current conversion. The A/D Result register
pair will NOT be updated with the partially completed
A/D conversion sample. That is, the ADRESH:ADRESL
registers will continue to contain the value of the last
completed conversion (or the last value written to the
ADRESH:ADRESL registers). After the A/D conversion
is aborted, the next acquisition on the selected channel
is automatically started. The GO/DONE bit can then be
set to start the conversion.
In Figure 11-3, after the GO bit is set, the first time
segment has a minimum of TCY and a maximum of TAD.
FIGURE 11-3: A/D CONVERSION TAD CYCLES
TAD1 TAD2 TAD3 TAD4 TAD5 TAD6 TAD7 TAD8 TAD9
b9 b8 b7 b6 b5 b4 b3 b2
TCY to TAD
Conversion starts
Holding capacitor is disconnected from analog input (typically 100 ns)
Set GO bit
11.4.1 A/D RESULT REGISTERS
The ADRESH:ADRESL register pair is the location
where the 10-bit A/D result is loaded at the completion
of the A/D conversion. This register pair is 16 bits wide.
The A/D module gives the flexibility to left or right justify
the 10-bit result in the 16-bit result register. The A/D
Note: The GO/DONE bit should NOT be set in
the same instruction that turns on the A/D.
TAD10 TAD11
b1 b0
ADRES is loaded
GO bit is cleared
ADIF bit is set
Holding capacitor is connected to analog input
Format Select bit (ADFM) controls this justification.
Figure 11-4 shows the operation of the A/D result
justification. The extra bits are loaded with ‘0’s. When
an A/D result will not overwrite these locations (A/D dis-able),
these registers may be used as two general
purpose 8-bit registers.
FIGURE 11-4: A/D RESULT JUSTIFICATION
10-bit Result
ADFM = 1
7 2 1 0 7 0
0000 00
ADRESH ADRESL
ADFM = 0
10-bit Result
7 0 7 6 5 0
0000 00
ADRESH ADRESL
10-bit Result
Right Justified Left Justified

PIC16F87XA
11.5 A/D Operation During Sleep
The A/D module can operate during Sleep mode. This
requires that the A/D clock source be set to RC
(ADCS1:ADCS0 = 11). When the RC clock source is
selected, the A/D module waits one instruction cycle
before starting the conversion. This allows the SLEEP
instruction to be executed which eliminates all digital
switching noise from the conversion. When the conver-sion
is completed, the GO/DONE bit will be cleared and
the result loaded into the ADRES register. If the A/D
interrupt is enabled, the device will wake-up from
Sleep. If the A/D interrupt is not enabled, the A/D mod-ule
will then be turned off, although the ADON bit will
remain set.
When the A/D clock source is another clock option (not
RC), a SLEEP instruction will cause the present conver-sion
to be aborted and the A/D module to be turned off,
though the ADON bit will remain set.
Turning off the A/D places the A/D module in its lowest
current consumption state.
Note: For the A/D module to operate in Sleep,
the A/D clock source must be set to RC
(ADCS1:ADCS0 = 11). To allow the con-version
to occur during Sleep, ensure the
SLEEP instruction immediately follows the
instruction that sets the GO/DONE bit.
11.6 Effects of a Reset
A device Reset forces all registers to their Reset state.
This forces the A/D module to be turned off and any
conversion is aborted. All A/D input pins are configured
as analog inputs.
The value that is in the ADRESH:ADRESL registers is
not modified for a Power-on Reset. The
ADRESH:ADRESL registers will contain unknown data
after a Power-on Reset.
TABLE 11-2: REGISTERS/BITS ASSOCIATED WITH A/D
Value on
POR, BOR
Value on
MCLR, WDT
0Bh,8Bh,
10Bh,18Bh
1Eh ADRESH A/D Result Register High Byte xxxx xxxx uuuu uuuu
9Eh ADRESL A/D Result Register Low Byte xxxx xxxx uuuu uuuu
1Fh ADCON0 ADCS1 ADCS0 CHS2 CHS1 CHS0 GO/DONE — ADON 0000 00-0 0000 00-0
05h PORTA — — PORTA Data Latch when written: PORTA pins when read --0x 0000 --0u 0000
89h(1) TRISE IBF OBF IBOV PSPMODE — PORTE Data Direction bits 0000 -111 0000 -111
09h(1) PORTE — — — — — RE2 RE1 RE0 ---- -xxx ---- -uuu
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are not used for A/D conversion.
Note 1: These registers are not available on 28-pin devices.

PIC16F87XA
NOTES:

PIC16F87XA
12.0 COMPARATOR MODULE
The comparator module contains two analog compara-tors.
The inputs to the comparators are multiplexed
with I/O port pins RA0 through RA3, while the outputs
are multiplexed to pins RA4 and RA5. The on-chip volt-age
reference (Section 13.0 “Comparator Voltage
Reference Module”) can also be an input to the
comparators.
The CMCON register (Register 12-1) controls the com-parator
input and output multiplexers. A block diagram
of the various comparator configurations is shown in
Figure 12-1.
REGISTER 12-1: CMCON REGISTER
R-0 R-0 R/W-0 R/W-0 R/W-0 R/W-1 R/W-1 R/W-1
C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0
bit 7 bit 0
bit 7 C2OUT: Comparator 2 Output bit
When C2INV = 0:
1 = C2 VIN+ > C2 VIN-
0 = C2 VIN+ < C2 VIN-When
C2INV = 1:
1 = C2 VIN+ < C2 VIN-
0 = C2 VIN+ > C2 VIN-bit
6 C1OUT: Comparator 1 Output bit
When C1INV = 0:
1 = C1 VIN+ > C1 VIN-
0 = C1 VIN+ < C1 VIN-When
C1INV = 1:
1 = C1 VIN+ < C1 VIN-
0 = C1 VIN+ > C1 VIN-bit
5 C2INV: Comparator 2 Output Inversion bit
1 = C2 output inverted
0 = C2 output not inverted
bit 4 C1INV: Comparator 1 Output Inversion bit
1 = C1 output inverted
0 = C1 output not inverted
bit 3 CIS: Comparator Input Switch bit
When CM2:CM0 = 110:
1 = C1 VIN- connects to RA3/AN3
C2 VIN- connects to RA2/AN2
0 = C1 VIN- connects to RA0/AN0
C2 VIN- connects to RA1/AN1
bit 2 CM2:CM0: Comparator Mode bits
Figure 12-1 shows the Comparator modes and CM2:CM0 bit settings.
Legend:

PIC16F87XA
12.1 Comparator Configuration
There are eight modes of operation for the compara-tors.
The CMCON register is used to select these
modes. Figure 12-1 shows the eight possible modes.
The TRISA register controls the data direction of the
comparator pins for each mode. If the Comparator
mode is changed, the comparator output level may not
be valid for the specified mode change delay shown in
Section 17.0 “Electrical Characteristics”.
Note: Comparator interrupts should be disabled
FIGURE 12-1: COMPARATOR I/O OPERATING MODES
during a Comparator mode change.
Otherwise, a false interrupt may occur.
C1
Comparators Reset
CM2:CM0 = 000
A
RA0/AN0 VIN-RA3/
AN3 VIN+
Off (Read as ‘0’)
A
C2
A
RA1/AN1 VIN-RA2/
AN2 VIN+
A
Two Independent Comparators
C1
CM2:CM0 = 010
A
RA0/AN0 VIN-RA3/
AN3 VIN+
C1OUT
A
C2
A
RA1/AN1 VIN-RA2/
AN2 VIN+
C2OUT
A
Two Common Reference Comparators
C1
CM2:CM0 = 100
A
RA0/AN0 VIN-RA3/
AN3 VIN+
C1OUT
A
C2
A
RA1/AN1 VIN-RA2/
AN2 VIN+
C2OUT
D
One Independent Comparator with Output
C1
C2
CM2:CM0 = 001
A
RA0/AN0 VIN-RA3/
AN3 A
VIN+
RA4/T0CKI/C1OUT
D
RA1/AN1 VIN-RA2/
AN2 VIN+
C1OUT
D
Comparators Off (POR Default Value)
C1
CM2:CM0 = 111
D
RA0/AN0 VIN-RA3/
AN3 VIN+
D
C2
D
RA1/AN1 VIN-RA2/
AN2 VIN+
D
Two Independent Comparators with Outputs
C1
CM2:CM0 = 011
A
RA0/AN0 VIN-RA3/
AN3 VIN+
C1OUT
A
C2
RA4/T0CKI/C1OUT
A
RA1/AN1 VIN-RA2/
AN2 VIN+
C2OUT
A
RA5/AN4/SS/C2OUT
Two Common Reference Comparators with Outputs
C1
CM2:CM0 = 101
A
RA0/AN0 VIN-RA3/
AN3 VIN+
C1OUT
A
C2
RA4/T0CKI/C1OUT
A
RA1/AN1 VIN-RA2/
AN2 VIN+
C2OUT
D
RA5/AN4/SS/C2OUT
Four Inputs Multiplexed to Two Comparators
CM2:CM0 = 110
A
RA0/AN0 VIN-VIN+
RA3/AN3 C1OUT
C1
A
A
CIS = 0
CIS = 1
RA1/AN1 VIN-VIN+
RA2/AN2 C2OUT
C2
A
From Comparator
CIS = 0
CIS = 1
CVREF
VREF Module
A = Analog Input, port reads zeros always. D = Digital Input. CIS (CMCON<3>) is the Comparator Input Switch.

PIC16F87XA
12.2 Comparator Operation
A single comparator is shown in Figure 12-2 along with
the relationship between the analog input levels and
the digital output. When the analog input at VIN+ is less
than the analog input VIN-, the output of the comparator
is a digital low level. When the analog input at VIN+ is
greater than the analog input VIN-, the output of the
comparator is a digital high level. The shaded areas of
the output of the comparator in Figure 12-2 represent
the uncertainty due to input offsets and response time.
12.3 Comparator Reference
An external or internal reference signal may be used
depending on the comparator operating mode. The
analog signal present at VIN- is compared to the signal
at VIN+ and the digital output of the comparator is
adjusted accordingly (Figure 12-2).
FIGURE 12-2: SINGLE COMPARATOR
VIN+ +
VIN-Output
–
VIN-Note
VIN–
VIN+
VIN+
OOuuttppuutt
12.3.1 EXTERNAL REFERENCE SIGNAL
When external voltage references are used, the
comparator module can be configured to have the com-parators
operate from the same or different reference
sources. However, threshold detector applications may
require the same reference. The reference signal must
be between VSS and VDD and can be applied to either
pin of the comparator(s).
12.3.2 INTERNAL REFERENCE SIGNAL
The comparator module also allows the selection of an
internally generated voltage reference for the compara-tors.
Section 13.0 “Comparator Voltage Reference
Module” contains a detailed description of the Compar-ator
Voltage Reference module that provides this signal.
The internal reference signal is used when comparators
are in mode, CM<2:0> = 110 (Figure 12-1). In this
mode, the internal voltage reference is applied to the
VIN+ pin of both comparators.
12.4 Comparator Response Time
Response time is the minimum time, after selecting a
new reference voltage or input source, before the com-parator
output has a valid level. If the internal reference
is changed, the maximum delay of the internal voltage
reference must be considered when using the compar-ator
outputs. Otherwise, the maximum delay of the
comparators should be used (Section 17.0 “Electrical
Characteristics”).
12.5 Comparator Outputs
The comparator outputs are read through the CMCON
register. These bits are read-only. The comparator
outputs may also be directly output to the RA4 and RA5
I/O pins. When enabled, multiplexors in the output path
of the RA4 and RA5 pins will switch and the output of
each pin will be the unsynchronized output of the com-parator.
The uncertainty of each of the comparators is
related to the input offset voltage and the response time
given in the specifications. Figure 12-3 shows the
comparator output block diagram.
The TRISA bits will still function as an output enable/
disable for the RA4 and RA5 pins while in this mode.
The polarity of the comparator outputs can be changed
using the C2INV and C1INV bits (CMCON<4:5>).
1: When reading the Port register, all pins
configured as analog inputs will read as a
‘0’. Pins configured as digital inputs will
convert an analog input according to the
Schmitt Trigger input specification.
2: Analog levels on any pin defined as a dig-ital
input may cause the input buffer to
consume more current than is specified.
3: RA4 is an open collector I/O pin. When
used as an output, a pull-up resistor is
required.

PIC16F87XA
FIGURE 12-3: COMPARATOR OUTPUT BLOCK DIAGRAM
To RA4 or
RA5 Pin
Bus
Data
Read CMCON
Set
CMIF
bit
From
Other
Comparator
12.6 Comparator Interrupts
The comparator interrupt flag is set whenever there is
a change in the output value of either comparator.
Software will need to maintain information about the
status of the output bits, as read from CMCON<7:6>, to
determine the actual change that occurred. The CMIF
bit (PIR registers) is the Comparator Interrupt Flag. The
CMIF bit must be reset by clearing it (‘0’). Since it is
also possible to write a ‘1’ to this register, a simulated
interrupt may be initiated.
The CMIE bit (PIE registers) and the PEIE bit (INTCON
register) must be set to enable the interrupt. In addition,
the GIE bit must also be set. If any of these bits are
clear, the interrupt is not enabled, though the CMIF bit
will still be set if an interrupt condition occurs.
Q D
Port Pins
MULTIPLEX
+ -
Q D
EN
CL
Read CMCON
Reset
CxINV
Note: If a change in the CMCON register
(C1OUT or C2OUT) should occur when a
read operation is being executed (start of
the Q2 cycle), then the CMIF (PIR
registers) interrupt flag may not get set.
The user, in the Interrupt Service Routine, can clear the
interrupt in the following manner:
a) Any read or write of CMCON will end the
mismatch condition.
b) Clear flag bit CMIF.
A mismatch condition will continue to set flag bit CMIF.
Reading CMCON will end the mismatch condition and
allow flag bit CMIF to be cleared.
EN

PIC16F87XA
12.7 Comparator Operation During
Sleep
When a comparator is active and the device is placed
in Sleep mode, the comparator remains active and the
interrupt is functional if enabled. This interrupt will
wake-up the device from Sleep mode when enabled.
While the comparator is powered up, higher Sleep
currents than shown in the power-down current
specification will occur. Each operational comparator
will consume additional current as shown in the com-parator
specifications. To minimize power consumption
while in Sleep mode, turn off the comparators,
CM<2:0> = 111, before entering Sleep. If the device
wakes up from Sleep, the contents of the CMCON
register are not affected.
12.8 Effects of a Reset
A device Reset forces the CMCON register to its Reset
state, causing the comparator module to be in the
Comparator Off mode, CM<2:0> = 111. This ensures
compatibility to the PIC16F87X devices.
12.9 Analog Input Connection
Considerations
A simplified circuit for an analog input is shown in
Figure 12-4. Since the analog pins are connected to a
digital output, they have reverse biased diodes to VDD
and VSS. The analog input, therefore, must be between
VSS and VDD. If the input voltage deviates from this
range by more than 0.6V in either direction, one of the
diodes is forward biased and a latch-up condition may
occur. A maximum source impedance of 10 kΩ is rec-ommended
for the analog sources. Any external com-ponent
connected to an analog input pin, such as a
capacitor or a Zener diode, should have very little
leakage current.
FIGURE 12-4: ANALOG INPUT MODEL
VA
RS < 10K
AIN
CPIN
5 pF
VDD
VT = 0.6 V
VT = 0.6 V
RIC
ILEAKAGE
±500 nA
VSS
Legend: CPIN = Input Capacitance
VT = Threshold Voltage
ILEAKAGE = Leakage Current at the pin due to various junctions
RIC = Interconnect Resistance
RS = Source Impedance
VA = Analog Voltage

PIC16F87XA
TABLE 12-1: REGISTERS ASSOCIATED WITH COMPARATOR MODULE
Value on
POR
Value on
all other
Resets
0Bh, 8Bh,
INTCON GIE/
PEIE/
TMR0IE INTIE RBIE TMR0IF INTIF RBIF 0000 000x 0000 000u
10Bh,18Bh
GIEH
GIEL
0Dh PIR2 — CMIF — — BCLIF LVDIF TMR3IF CCP2IF -0-- 0000 -0-- 0000
8Dh PIE2 — CMIE — — BCLIE LVDIE TMR3IE CCP2IE -0-- 0000 -0-- 0000
05h PORTA — — RA5 RA4 RA3 RA2 RA1 RA0 --0x 0000 --0u 0000
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are unused by the comparator module.

PIC16F87XA
13.0 COMPARATOR VOLTAGE
REFERENCE MODULE
The Comparator Voltage Reference Generator is a
16-tap resistor ladder network that provides a fixed
voltage reference when the comparators are in mode
‘110’. A programmable register controls the function of
the reference generator. Register 13-1 lists the bit
functions of the CVRCON register.
As shown in Figure 13-1, the resistor ladder is seg-mented
to provide two ranges of CVREF values and has
a power-down function to conserve power when the
reference is not being used. The comparator reference
supply voltage (also referred to as CVRSRC) comes
directly from VDD. It should be noted, however, that the
voltage at the top of the ladder is CVRSRC – VSAT,
where VSAT is the saturation voltage of the power
switch transistor. This reference will only be as
accurate as the values of CVRSRC and VSAT.
The output of the reference generator may be con-nected
to the RA2/AN2/VREF-/CVREF pin. This can be
used as a simple D/A function by the user if a very high-impedance
load is used. The primary purpose of this
function is to provide a test path for testing the
reference generator function.
REGISTER 13-1: CVRCON CONTROL REGISTER (ADDRESS 9Dh)
R/W-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0
CVREN CVROE CVRR — CVR3 CVR2 CVR1 CVR0
bit 7 bit 0
bit 7 CVREN: Comparator Voltage Reference Enable bit
1 = CVREF circuit powered on
0 = CVREF circuit powered down
bit 6 CVROE: Comparator VREF Output Enable bit
1 = CVREF voltage level is output on RA2/AN2/VREF-/CVREF pin
0 = CVREF voltage level is disconnected from RA2/AN2/VREF-/CVREF pin
bit 5 CVRR: Comparator VREF Range Selection bit
1 = 0 to 0.75 CVRSRC, with CVRSRC/24 step size
0 = 0.25 CVRSRC to 0.75 CVRSRC, with CVRSRC/32 step size
bit 3-0 CVR3:CVR0: Comparator VREF Value Selection bits 0 ≤ VR3:VR0 ≤ 15
When CVRR = 1:
CVREF = (VR<3:0>/ 24) • (CVRSRC)
When CVRR = 0:
CVREF = 1/4 • (CVRSRC) + (VR3:VR0/ 32) • (CVRSRC)
Legend:
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

PIC16F87XA
FIGURE 13-1: COMPARATOR VOLTAGE REFERENCE BLOCK DIAGRAM
8R CVRR
CVR3
CVR2
CVR1
CVR0
16 Stages
8R R R R R
16:1 Analog MUX
CVREN
RA2/AN2/VREF-/CVREF
CVREF
Input to
Comparator
VDD
CVROE
TABLE 13-1: REGISTERS ASSOCIATED WITH COMPARATOR VOLTAGE REFERENCE
Value on
POR
Value on
all other
Resets
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’.
Shaded cells are not used with the comparator voltage reference.

PIC16F87XA
14.0 SPECIAL FEATURES OF THE
CPU
All PIC16F87XA devices have a host of features
intended to maximize system reliability, minimize cost
through elimination of external components, provide
power saving operating modes and offer code
protection. These are:
• Oscillator Selection
• Reset
- Power-on Reset (POR)
- Power-up Timer (PWRT)
- Oscillator Start-up Timer (OST)
- Brown-out Reset (BOR)
• Interrupts
• Watchdog Timer (WDT)
• Sleep
• Code Protection
• ID Locations
• In-Circuit Serial Programming
• Low-Voltage In-Circuit Serial Programming
• In-Circuit Debugger
PIC16F87XA devices have a Watchdog Timer which
can be shut-off only through configuration bits. It runs
off its own RC oscillator for added reliability.
There are two timers that offer necessary delays on
power-up. One is the Oscillator Start-up Timer (OST),
intended to keep the chip in Reset until the crystal oscil-lator
is stable. The other is the Power-up Timer
(PWRT), which provides a fixed delay of 72 ms (nomi-nal)
on power-up only. It is designed to keep the part in
Reset while the power supply stabilizes. With these two
timers on-chip, most applications need no external
Reset circuitry.
Sleep mode is designed to offer a very low current
power-down mode. The user can wake-up from Sleep
through external Reset, Watchdog Timer wake-up or
through an interrupt.
Several oscillator options are also made available to
allow the part to fit the application. The RC oscillator
option saves system cost while the LP crystal option
saves power. A set of configuration bits is used to
select various options.
Additional information on special features is available
in the PICmicro® Mid-Range MCU Family Reference
Manual (DS33023).
14.1 Configuration Bits
The configuration bits can be programmed (read as ‘0’),
or left unprogrammed (read as ‘1’) to select various
device configurations. The erased or unprogrammed
value of the Configuration Word register is 3FFFh.
These bits are mapped in program memory location
2007h.
It is important to note that address 2007h is beyond the
user program memory space which can be accessed
only during programming.

PIC16F87XA
REGISTER 14-1: CONFIGURATION WORD (ADDRESS 2007h)(1)
R/P-1 U-0 R/P-1 R/P-1 R/P-1 R/P-1 R/P-1 R/P-1 U-0 U-0 R/P-1 R/P-1 R/P-1 R/P-1
CP — DEBUG WRT1 WRT0 CPD LVP BOREN — — PWRTEN WDTEN FOSC1 FOSC0
bit 13 bit0
bit 13 CP: Flash Program Memory Code Protection bit
1 = Code protection off
0 = All program memory code-protected
bit 11 DEBUG: In-Circuit Debugger Mode bit
1 = In-Circuit Debugger disabled, RB6 and RB7 are general purpose I/O pins
0 = In-Circuit Debugger enabled, RB6 and RB7 are dedicated to the debugger
bit 10-9 WRT1:WRT0 Flash Program Memory Write Enable bits
For PIC16F876A/877A:
11 = Write protection off; all program memory may be written to by EECON control
10 = 0000h to 00FFh write-protected; 0100h to 1FFFh may be written to by EECON control
00 = 0000h to 0FFFh write-protected; 1000h to 1FFFh may be written to by EECON control
For PIC16F873A/874A:
11 = Write protection off; all program memory may be written to by EECON control
bit 8 CPD: Data EEPROM Memory Code Protection bit
1 = Data EEPROM code protection off
0 = Data EEPROM code-protected
bit 7 LVP: Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit
1 = RB3/PGM pin has PGM function; low-voltage programming enabled
0 = RB3 is digital I/O, HV on MCLR must be used for programming
bit 6 BOREN: Brown-out Reset Enable bit
1 = BOR enabled
0 = BOR disabled
bit 3 PWRTEN: Power-up Timer Enable bit
1 = PWRT disabled
0 = PWRT enabled
bit 2 WDTEN: Watchdog Timer Enable bit
1 = WDT enabled
0 = WDT disabled
bit 1-0 FOSC1:FOSC0: Oscillator Selection bits
11 = RC oscillator
10 = HS oscillator
01 = XT oscillator
00 = LP oscillator
Legend:
R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’
- n = Value when device is unprogrammed u = Unchanged from programmed state
Note 1: The erased (unprogrammed) value of the Configuration Word is 3FFFh.

PIC16F87XA
14.2 Oscillator Configurations
14.2.1 OSCILLATOR TYPES
The PIC16F87XA can be operated in four different
oscillator modes. The user can program two configura-tion
bits (FOSC1 and FOSC0) to select one of these four
modes:
• LP Low-Power Crystal
• XT Crystal/Resonator
• HS High-Speed Crystal/Resonator
• RC Resistor/Capacitor
14.2.2 CRYSTAL OSCILLATOR/CERAMIC
RESONATORS
In XT, LP or HS modes, a crystal or ceramic resonator
is connected to the OSC1/CLKI and OSC2/CLKO pins
to establish oscillation (Figure 14-1). The PIC16F87XA
oscillator design requires the use of a parallel cut crys-tal.
Use of a series cut crystal may give a frequency out
of the crystal manufacturer’s specifications. When in
XT, LP or HS modes, the device can have an external
clock source to drive the OSC1/CLKI pin (Figure 14-2).
FIGURE 14-1: CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP
OSC CONFIGURATION)
FIGURE 14-2: EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR
LP OSC CONFIGURATION)
OSC1
Clock from
Ext. System PIC16F87XA
Open OSC2
TABLE 14-1: CERAMIC RESONATORS
C1(1)
C2(1)
XTAL
OSC1
OSC2
RF(3)
Sleep
To
Logic
Internal
PIC16F87XA
Rs
(2)
Note 1: See Table 14-1 and Table 14-2 for recommended
values of C1 and C2.
2: A series resistor (Rs) may be required for AT
strip cut crystals.
3: RF varies with the crystal chosen.
Ranges Tested:
Mode Freq. OSC1 OSC2
XT 455 kHz
2.0 MHz
4.0 MHz
68-100 pF
15-68 pF
15-68 pF
68-100 pF
15-68 pF
15-68 pF
HS 8.0 MHz
16.0 MHz
10-68 pF
10-22 pF
10-68 pF
10-22 pF
See notes following Table 14-2.
Resonators Used:
2.0 MHz Murata Erie CSA2.00MG ± 0.5%
4.0 MHz Murata Erie CSA4.00MG ± 0.5%
8.0 MHz Murata Erie CSA8.00MT ± 0.5%
16.0 MHz Murata Erie CSA16.00MX ± 0.5%
All resonators used did not have built-in capacitors.

PIC16F87XA
TABLE 14-2: CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
14.2.3 RC OSCILLATOR
For timing insensitive applications, the “RC” device
option offers additional cost savings. The RC oscillator
frequency is a function of the supply voltage, the
resistor (REXT) and capacitor (CEXT) values and the
operating temperature. In addition to this, the oscillator
frequency will vary from unit to unit due to normal pro-cess
parameter variation. Furthermore, the difference
in lead frame capacitance between package types will
also affect the oscillation frequency, especially for low
CEXT values. The user also needs to take into account
variation due to tolerance of external R and C
components used. Figure 14-3 shows how the R/C
combination is connected to the PIC16F87XA.
FIGURE 14-3: RC OSCILLATOR MODE
Osc Type
Crystal
Freq.
Cap. Range
C1
Cap. Range
C2
LP 32 kHz 33 pF 33 pF
200 kHz 15 pF 15 pF
XT 200 kHz 47-68 pF 47-68 pF
1 MHz 15 pF 15 pF
4 MHz 15 pF 15 pF
HS 4 MHz 15 pF 15 pF
8 MHz 15-33 pF 15-33 pF
20 MHz 15-33 pF 15-33 pF
See notes following this table.
Crystals Used
32 kHz Epson C-001R32.768K-A ± 20 PPM
200 kHz STD XTL 200.000KHz ± 20 PPM
1 MHz ECS ECS-10-13-1 ± 50 PPM
4 MHz ECS ECS-40-20-1 ± 50 PPM
8 MHz EPSON CA-301 8.000M-C ± 30 PPM
20 MHz EPSON CA-301 20.000M-C ± 30 PPM
Note 1: Higher capacitance increases the stability
of oscillator but also increases the start-up
time.
2: Since each resonator/crystal has its own
characteristics, the user should consult
the resonator/crystal manufacturer for
appropriate values of external
components.
3: Rs may be required in HS mode, as well
as XT mode, to avoid overdriving crystals
with low drive level specification.
4: When migrating from other PICmicro®
devices, oscillator performance should be
verified.
OSC1
OSC2/CLKO
VDD
REXT
CEXT
Internal
Clock
PIC16F87XA
FOSC/4
VSS
Recommended values: 3 kΩ ≤ REXT ≤ 100 kΩ
CEXT > 20 pF

PIC16F87XA
14.3 Reset
The PIC16F87XA differentiates between various kinds
of Reset:
• Power-on Reset (POR)
• MCLR Reset during normal operation
• MCLR Reset during Sleep
• WDT Reset (during normal operation)
• WDT Wake-up (during Sleep)
• Brown-out Reset (BOR)
Some registers are not affected in any Reset condition.
Their status is unknown on POR and unchanged in any
other Reset. Most other registers are reset to a “Reset
state” on Power-on Reset (POR), on the MCLR and
WDT Reset, on MCLR Reset during Sleep and Brown-out
Reset (BOR). They are not affected by a WDT
wake-up which is viewed as the resumption of normal
operation. The TO and PD bits are set or cleared differ-ently
in different Reset situations as indicated in
Table 14-4. These bits are used in software to deter-mine
the nature of the Reset. See Table 14-6 for a full
description of Reset states of all registers.
A simplified block diagram of the on-chip Reset circuit
is shown in Figure 14-4.
FIGURE 14-4: SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT
S
R Q
External
Reset
MCLR
VDD
OSC1
WDT
Module
VDD Rise
Detect
Brown-out
Reset BODEN
OST/PWRT
(1)
On-chip
RC OSC
Sleep
WDT
Time-out
Reset
Power-on Reset
OST
10-bit Ripple Counter
PWRT
Chip_Reset
10-bit Ripple Counter
Enable PWRT
Enable OST
Note 1: This is a separate oscillator from the RC oscillator of the CLKI pin.

PIC16F87XA
14.4 MCLR
PIC16F87XA devices have a noise filter in the MCLR
Reset path. The filter will detect and ignore small
pulses.
It should be noted that a WDT Reset does not drive
MCLR pin low.
The behavior of the ESD protection on the MCLR pin
differs from previous devices of this family. Voltages
applied to the pin that exceed its specification can
result in both Resets and current consumption outside
of device specification during the Reset event. For this
reason, Microchip recommends that the MCLR pin no
longer be tied directly to VDD. The use of an RCR
network, as shown in Figure 14-5, is suggested.
FIGURE 14-5: RECOMMENDED MCLR
CIRCUIT
R1(1)
C1
VDD
PIC16F87XA
MCLR
R2(2)
Note 1: R1 < 40 kΩ is recommended to make
sure that the voltage drop across R does
not violate the device’s electrical
specification.
2: R2 > than 1K will limit any current
flowing into MCLR from the external
capacitor C, in the event of MCLR/VPP
breakdown due to Electrostatic
Discharge (ESD) or Electrical
Overstress (EOS).
14.5 Power-on Reset (POR)
A Power-on Reset pulse is generated on-chip when
VDD rise is detected (in the range of 1.2V-1.7V). To take
advantage of the POR, tie the MCLR pin to VDD
through an RC network, as described in Section 14.4
“MCLR”. A maximum rise time for VDD is specified.
See Section 17.0 “Electrical Characteristics” for
details.
When the device starts normal operation (exits the
Reset condition), device operating parameters (volt-age,
frequency, temperature, etc.) must be met to
ensure operation. If these conditions are not met, the
device must be held in Reset until the operating condi-tions
are met. Brown-out Reset may be used to meet
the start-up conditions. For additional information, refer
to application note, AN607, “Power-up Trouble
Shooting” (DS00607).
14.6 Power-up Timer (PWRT)
The Power-up Timer provides a fixed 72 ms nominal
time-out on power-up only from the POR. The Power-up
Timer operates on an internal RC oscillator. The
chip is kept in Reset as long as the PWRT is active. The
PWRT’s time delay allows VDD to rise to an acceptable
level. A configuration bit is provided to enable or
disable the PWRT.
The power-up time delay will vary from chip to chip due
to VDD, temperature and process variation. See
Section 17.0 “Electrical Characteristics” for details
(TPWRT, parameter #33).
14.7 Oscillator Start-up Timer (OST)
The Oscillator Start-up Timer (OST) provides a delay of
1024 oscillator cycles (from OSC1 input) after the
PWRT delay is over (if PWRT is enabled). This helps to
ensure that the crystal oscillator or resonator has
started and stabilized.
The OST time-out is invoked only for XT, LP and HS
modes and only on Power-on Reset or wake-up from
Sleep.
14.8 Brown-out Reset (BOR)
The configuration bit, BODEN, can enable or disable
the Brown-out Reset circuit. If VDD falls below VBOR
(parameter D005, about 4V) for longer than TBOR
(parameter #35, about 100 μS), the brown-out situation
will reset the device. If VDD falls below VBOR for less
than TBOR, a Reset may not occur.
Once the brown-out occurs, the device will remain in
Brown-out Reset until VDD rises above VBOR. The
Power-up Timer then keeps the device in Reset for
TPWRT (parameter #33, about 72 mS). If VDD should
fall below VBOR during TPWRT, the Brown-out Reset
process will restart when VDD rises above VBOR with
the Power-up Timer Reset. The Power-up Timer is
always enabled when the Brown-out Reset circuit is
enabled, regardless of the state of the PWRT
configuration bit.
14.9 Time-out Sequence
On power-up, the time-out sequence is as follows: the
PWRT delay starts (if enabled) when a POR Reset
occurs. Then, OST starts counting 1024 oscillator
cycles when PWRT ends (LP, XT, HS). When the OST
ends, the device comes out of Reset.
If MCLR is kept low long enough, the time-outs will
expire. Bringing MCLR high will begin execution
immediately. This is useful for testing purposes or to
synchronize more than one PIC16F87XA device
operating in parallel.
Table 14-5 shows the Reset conditions for the Status,
PCON and PC registers, while Table 14-6 shows the
Reset conditions for all the registers.

PIC16F87XA
14.10 Power Control/Status Register
(PCON)
The Power Control/Status Register, PCON, has up to
two bits depending upon the device.
Bit 0 is the Brown-out Reset Status bit, BOR. The BOR
bit is unknown on a Power-on Reset. It must then be set
by the user and checked on subsequent Resets to see if
it has been cleared, indicating that a BOR has occurred.
When the Brown-out Reset is disabled, the state of the
BOR bit is unpredictable and is, therefore, not valid at
any time.
Bit 1 is the Power-on Reset Status bit, POR. It is
cleared on a Power-on Reset and unaffected other-wise.
The user must set this bit following a Power-on
Reset.
TABLE 14-3: TIME-OUT IN VARIOUS SITUATIONS
Oscillator Configuration
Power-up
PWRTE = 0 PWRTE = 1 Sleep
XT, HS, LP 72 ms + 1024 TOSC 1024 TOSC 72 ms + 1024 TOSC 1024 TOSC
RC 72 ms — 72 ms —
TABLE 14-4: STATUS BITS AND THEIR SIGNIFICANCE
POR BOR TO PD Condition
0 x 1 1 Power-on Reset
0 x 0 x Illegal, TO is set on POR
0 x x 0 Illegal, PD is set on POR
1 0 1 1 Brown-out Reset
1 1 0 1 WDT Reset
1 1 0 0 WDT Wake-up
1 1 u u MCLR Reset during normal operation
1 1 1 0 MCLR Reset during Sleep or Interrupt Wake-up from Sleep
Legend: x = don’t care, u = unchanged
TABLE 14-5: RESET CONDITIONS FOR SPECIAL REGISTERS
Brown-out
Wake-up from
Condition
Program
Counter
Status
Register
PCON
Register
Power-on Reset 000h 0001 1xxx ---- --0x
MCLR Reset during normal operation 000h 000u uuuu ---- --uu
MCLR Reset during Sleep 000h 0001 0uuu ---- --uu
WDT Reset 000h 0000 1uuu ---- --uu
WDT Wake-up PC + 1 uuu0 0uuu ---- --uu
Brown-out Reset 000h 0001 1uuu ---- --u0
Interrupt Wake-up from Sleep PC + 1(1) uuu1 0uuu ---- --uu
Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’
Note 1: When the wake-up is due to an interrupt and the GIE bit is set, the PC is loaded with the interrupt vector
(0004h).

PIC16F87XA
TABLE 14-6: INITIALIZATION CONDITIONS FOR ALL REGISTERS
Register Devices
Power-on Reset,
Brown-out Reset
MCLR Resets,
WDT Reset
Wake-up via WDT or
Interrupt
W 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
INDF 73A 74A 76A 77A N/A N/A N/A
TMR0 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
PCL 73A 74A 76A 77A 0000 0000 0000 0000 PC + 1(2)
STATUS 73A 74A 76A 77A 0001 1xxx 000q quuu(3) uuuq quuu(3)
FSR 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
PORTA 73A 74A 76A 77A --0x 0000 --0u 0000 --uu uuuu
PORTB 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
PORTC 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
PORTD 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
PORTE 73A 74A 76A 77A ---- -xxx ---- -uuu ---- -uuu
PCLATH 73A 74A 76A 77A ---0 0000 ---0 0000 ---u uuuu
INTCON 73A 74A 76A 77A 0000 000x 0000 000u uuuu uuuu(1)
PIR1
73A 74A 76A 77A r000 0000 r000 0000 ruuu uuuu(1)
73A 74A 76A 77A 0000 0000 0000 0000 uuuu uuuu(1)
PIR2 73A 74A 76A 77A -0-0 0--0 -0-0 0--0 -u-u u--u(1)
TMR1L 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
TMR1H 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
T1CON 73A 74A 76A 77A --00 0000 --uu uuuu --uu uuuu
TMR2 73A 74A 76A 77A 0000 0000 0000 0000 uuuu uuuu
T2CON 73A 74A 76A 77A -000 0000 -000 0000 -uuu uuuu
SSPBUF 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
SSPCON 73A 74A 76A 77A 0000 0000 0000 0000 uuuu uuuu
CCPR1L 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
CCPR1H 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
CCP1CON 73A 74A 76A 77A --00 0000 --00 0000 --uu uuuu
RCSTA 73A 74A 76A 77A 0000 000x 0000 000x uuuu uuuu
TXREG 73A 74A 76A 77A 0000 0000 0000 0000 uuuu uuuu
RCREG 73A 74A 76A 77A 0000 0000 0000 0000 uuuu uuuu
CCPR2L 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
CCPR2H 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
CCP2CON 73A 74A 76A 77A 0000 0000 0000 0000 uuuu uuuu
ADRESH 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
ADCON0 73A 74A 76A 77A 0000 00-0 0000 00-0 uuuu uu-u
OPTION_REG 73A 74A 76A 77A 1111 1111 1111 1111 uuuu uuuu
TRISA 73A 74A 76A 77A --11 1111 --11 1111 --uu uuuu
TRISB 73A 74A 76A 77A 1111 1111 1111 1111 uuuu uuuu
TRISC 73A 74A 76A 77A 1111 1111 1111 1111 uuuu uuuu
Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition,
r = reserved, maintain clear. Shaded cells indicate conditions do not apply for the designated device.
Note 1: One or more bits in INTCON, PIR1 and/or PIR2 will be affected (to cause wake-up).
2: When the wake-up is due to an interrupt and the GIE bit is set, the PC is loaded with the interrupt vector
(0004h).
3: See Table 14-5 for Reset value for specific condition.

PIC16F87XA
TABLE 14-6: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED)
Register Devices
Power-on Reset,
Brown-out Reset
MCLR Resets,
WDT Reset
Wake-up via WDT or
Interrupt
TRISD 73A 74A 76A 77A 1111 1111 1111 1111 uuuu uuuu
TRISE 73A 74A 76A 77A 0000 -111 0000 -111 uuuu -uuu
PIE1
73A 74A 76A 77A r000 0000 r000 0000 ruuu uuuu
73A 74A 76A 77A 0000 0000 0000 0000 uuuu uuuu
PIE2 73A 74A 76A 77A -0-0 0--0 -0-0 0--0 -u-u u--u
PCON 73A 74A 76A 77A ---- --qq ---- --uu ---- --uu
SSPCON2 73A 74A 76A 77A 0000 0000 0000 0000 uuuu uuuu
PR2 73A 74A 76A 77A 1111 1111 1111 1111 1111 1111
SSPADD 73A 74A 76A 77A 0000 0000 0000 0000 uuuu uuuu
SSPSTAT 73A 74A 76A 77A --00 0000 --00 0000 --uu uuuu
TXSTA 73A 74A 76A 77A 0000 -010 0000 -010 uuuu -uuu
SPBRG 73A 74A 76A 77A 0000 0000 0000 0000 uuuu uuuu
CMCON 73A 974 76A 77A 0000 0111 0000 0111 uuuu uuuu
CVRCON 73A 74A 76A 77A 000- 0000 000- 0000 uuu- uuuu
ADRESL 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
ADCON1 73A 74A 76A 77A 00-- 0000 00-- 0000 uu-- uuuu
EEDATA 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
EEADR 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
EEDATH 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
EEADRH 73A 74A 76A 77A xxxx xxxx uuuu uuuu uuuu uuuu
EECON1 73A 74A 76A 77A x--- x000 u--- u000 u--- uuuu
EECON2 73A 74A 76A 77A ---- ---- ---- ---- ---- ----
Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition,
r = reserved, maintain clear. Shaded cells indicate conditions do not apply for the designated device.
Note 1: One or more bits in INTCON, PIR1 and/or PIR2 will be affected (to cause wake-up).
2: When the wake-up is due to an interrupt and the GIE bit is set, the PC is loaded with the interrupt vector
(0004h).
3: See Table 14-5 for Reset value for specific condition.
FIGURE 14-6: TIME-OUT SEQUENCE ON POWER-UP (MCLR TIED TO VDD VIA RC NETWORK)
TPWRT
TOST
VDD
MCLR
Internal POR
PWRT Time-out
OST Time-out
Internal Reset

PIC16F87XA
FIGURE 14-7: TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO VDD): CASE 1
TPWRT
TOST
VDD
MCLR
Internal POR
PWRT Time-out
OST Time-out
Internal Reset
FIGURE 14-8: TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO VDD): CASE 2
VDD
MCLR
Internal POR
PWRT Time-out
OST Time-out
Internal Reset
TPWRT
TOST
FIGURE 14-9: SLOW RISE TIME (MCLR TIED TO VDD VIA RC NETWORK)
VDD
MCLR
Internal POR
PWRT Time-out
OST Time-out
Internal Reset
0V 1V
5V
TPWRT
TOST

PIC16F87XA
14.11 Interrupts
The PIC16F87XA family has up to 15 sources of
interrupt. The Interrupt Control register (INTCON)
records individual interrupt requests in flag bits. It also
has individual and global interrupt enable bits.
Note: Individual interrupt flag bits are set regard-less
of the status of their corresponding
mask bit or the GIE bit.
A global interrupt enable bit, GIE (INTCON<7>),
enables (if set) all unmasked interrupts or disables (if
cleared) all interrupts. When bit GIE is enabled and an
interrupt’s flag bit and mask bit are set, the interrupt will
vector immediately. Individual interrupts can be
disabled through their corresponding enable bits in
various registers. Individual interrupt bits are set
regardless of the status of the GIE bit. The GIE bit is
cleared on Reset.
The “return from interrupt” instruction, RETFIE, exits
the interrupt routine, as well as sets the GIE bit, which
re-enables interrupts.
The RB0/INT pin interrupt, the RB port change interrupt
and the TMR0 overflow interrupt flags are contained in
the INTCON register.
The peripheral interrupt flags are contained in the
Special Function Registers, PIR1 and PIR2. The
corresponding interrupt enable bits are contained in
Special Function Registers, PIE1 and PIE2, and the
peripheral interrupt enable bit is contained in Special
Function Register, INTCON.
When an interrupt is responded to, the GIE bit is
cleared to disable any further interrupt, the return
address is pushed onto the stack and the PC is loaded
with 0004h. Once in the Interrupt Service Routine, the
source(s) of the interrupt can be determined by polling
the interrupt flag bits. The interrupt flag bit(s) must be
cleared in software before re-enabling interrupts to
avoid recursive interrupts.
For external interrupt events, such as the INT pin or
PORTB change interrupt, the interrupt latency will be
three or four instruction cycles. The exact latency
depends when the interrupt event occurs. The latency
is the same for one or two-cycle instructions. Individual
interrupt flag bits are set regardless of the status of their
corresponding mask bit, PEIE bit or GIE bit.
FIGURE 14-10: INTERRUPT LOGIC
EEIF
EEIE
PSPIF(1)
PSPIE(1)
ADIF
ADIE
RCIF
RCIE
TXIF
TXIE
SSPIF
SSPIE
CCP1IF
CCP1IE
TMR2IF
TMR2IE
TMR1IF
TMR1IE
TMR0IF
TMR0IE
INTF
INTE
RBIF
RBIE
PEIE
GIE
Wake-up (If in Sleep mode)
Interrupt to CPU
CCP2IF
CCP2IE
BCLIF
BCLIE
CMIF
CMIE
Note 1: PSP interrupt is implemented only on PIC16F874A/877A devices.

PIC16F87XA
14.11.1 INT INTERRUPT
External interrupt on the RB0/INT pin is edge triggered,
either rising if bit INTEDG (OPTION_REG<6>) is set or
falling if the INTEDG bit is clear. When a valid edge
appears on the RB0/INT pin, flag bit, INTF
(INTCON<1>), is set. This interrupt can be disabled by
clearing enable bit, INTE (INTCON<4>). Flag bit INTF
must be cleared in software in the Interrupt Service
Routine before re-enabling this interrupt. The INT
interrupt can wake-up the processor from Sleep if bit
INTE was set prior to going into Sleep. The status of
global interrupt enable bit, GIE, decides whether or not
the processor branches to the interrupt vector following
wake-up. See Section 14.14 “Power-down Mode
(Sleep)” for details on Sleep mode.
14.11.2 TMR0 INTERRUPT
An overflow (FFh → 00h) in the TMR0 register will set
flag bit, TMR0IF (INTCON<2>). The interrupt can be
enabled/disabled by setting/clearing enable bit,
TMR0IE (INTCON<5>). See Section 5.0 “Timer0
Module”.
14.11.3 PORTB INTCON CHANGE
An input change on PORTB<7:4> sets flag bit, RBIF
(INTCON<0>). The interrupt can be enabled/disabled
by setting/clearing enable bit, RBIE (INTCON<4>). See
Section 4.2 “PORTB and the TRISB Register”.
14.12 Context Saving During Interrupts
During an interrupt, only the return PC value is saved
on the stack. Typically, users may wish to save key reg-isters
during an interrupt (i.e., W register and Status
register). This will have to be implemented in software.
For the PIC16F873A/874A devices, the register
W_TEMP must be defined in both Banks 0 and 1 and
must be defined at the same offset from the bank base
address (i.e., If W_TEMP is defined at 0x20 in Bank 0,
it must also be defined at 0xA0 in Bank 1). The regis-ters,
PCLATH_TEMP and STATUS_TEMP, are only
defined in Bank 0.
Since the upper 16 bytes of each bank are common in
the PIC16F876A/877A devices, temporary holding reg-isters,
W_TEMP, STATUS_TEMP and PCLATH_TEMP,
should be placed in here. These 16 locations don’t
require banking and therefore, make it easier for con-text
save and restore. The same code shown in
Example 14-1 can be used.
EXAMPLE 14-1: SAVING STATUS, W AND PCLATH REGISTERS IN RAM
MOVWF W_TEMP ;Copy W to TEMP register
SWAPF STATUS,W ;Swap status to be saved into W
CLRF STATUS ;bank 0, regardless of current bank, Clears IRP,RP1,RP0
MOVWF STATUS_TEMP ;Save status to bank zero STATUS_TEMP register
MOVF PCLATH, W ;Only required if using pages 1, 2 and/or 3
MOVWF PCLATH_TEMP ;Save PCLATH into W
CLRF PCLATH ;Page zero, regardless of current page
:
:(ISR) ;(Insert user code here)
:
MOVF PCLATH_TEMP, W ;Restore PCLATH
MOVWF PCLATH ;Move W into PCLATH
SWAPF STATUS_TEMP,W ;Swap STATUS_TEMP register into W
;(sets bank to original state)
MOVWF STATUS ;Move W into STATUS register
SWAPF W_TEMP,F ;Swap W_TEMP
SWAPF W_TEMP,W ;Swap W_TEMP into W

PIC16F87XA
14.13 Watchdog Timer (WDT)
The Watchdog Timer is a free running, on-chip RC
oscillator which does not require any external
components. This RC oscillator is separate from the
RC oscillator of the OSC1/CLKI pin. That means that
the WDT will run even if the clock on the OSC1/CLKI
and OSC2/CLKO pins of the device has been stopped,
for example, by execution of a SLEEP instruction.
During normal operation, a WDT time-out generates a
device Reset (Watchdog Timer Reset). If the device is
in Sleep mode, a WDT time-out causes the device to
wake-up and continue with normal operation (Watch-dog
Timer Wake-up). The TO bit in the Status register
will be cleared upon a Watchdog Timer time-out.
The WDT can be permanently disabled by clearing
configuration bit, WDTE (Section 14.1 “Configuration
Bits”).
WDT time-out period values may be found in
Section 17.0 “Electrical Characteristics” under
parameter #31. Values for the WDT prescaler (actually
a postscaler but shared with the Timer0 prescaler) may
be assigned using the OPTION_REG register.
Note 1: The CLRWDT and SLEEP instructions
FIGURE 14-11: WATCHDOG TIMER BLOCK DIAGRAM
2: When a CLRWDT instruction is executed
From TMR0 Clock Source
(Figure 5-1)
Postscaler
WDT Timer
WDT
Enable Bit
0
1 MUX
PSA
8
8-to-1 MUX PS2:PS0
0 1
MUX PSA
WDT
Time-out
Note: PSA and PS2:PS0 are bits in the OPTION_REG register.
TABLE 14-7: SUMMARY OF WATCHDOG TIMER REGISTERS
clear the WDT and the postscaler, if
assigned to the WDT and prevent it from
timing out and generating a device Reset
condition.
and the prescaler is assigned to the WDT,
the prescaler count will be cleared but the
prescaler assignment is not changed.
To TMR0 (Figure 5-1)
2007h Config. bits (1) BODEN(1) CP1 CP0 PWRTE(1) WDTE FOSC1 FOSC0
81h, 181h OPTION_REG RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0
Legend: Shaded cells are not used by the Watchdog Timer.
Note 1: See Register 14-1 for operation of these bits.

PIC16F87XA
14.14 Power-down Mode (Sleep)
Power-down mode is entered by executing a SLEEP
instruction.
If enabled, the Watchdog Timer will be cleared but
keeps running, the PD bit (Status<3>) is cleared, the
TO (Status<4>) bit is set and the oscillator driver is
turned off. The I/O ports maintain the status they had
before the SLEEP instruction was executed (driving
high, low or high-impedance).
For lowest current consumption in this mode, place all
I/O pins at either VDD or VSS, ensure no external
circuitry is drawing current from the I/O pin, power-down
the A/D and disable external clocks. Pull all I/O
pins that are high-impedance inputs, high or low
externally, to avoid switching currents caused by
floating inputs. The T0CKI input should also be at VDD
or VSS for lowest current consumption. The
contribution from on-chip pull-ups on PORTB should
also be considered.
The MCLR pin must be at a logic high level (VIHMC).
14.14.1 WAKE-UP FROM SLEEP
The device can wake-up from Sleep through one of the
following events:
1. External Reset input on MCLR pin.
2. Watchdog Timer wake-up (if WDT was enabled).
3. Interrupt from INT pin, RB port change or
peripheral interrupt.
External MCLR Reset will cause a device Reset. All other
events are considered a continuation of program execu-tion
and cause a “wake-up”. The TO and PD bits in the
Status register can be used to determine the cause of
device Reset. The PD bit, which is set on power-up, is
cleared when Sleep is invoked. The TO bit is cleared if a
WDT time-out occurred and caused wake-up.
The following peripheral interrupts can wake the device
from Sleep:
1. PSP read or write (PIC16F874/877 only).
2. TMR1 interrupt. Timer1 must be operating as an
asynchronous counter.
3. CCP Capture mode interrupt.
4. Special event trigger (Timer1 in Asynchronous
mode using an external clock).
5. SSP (Start/Stop) bit detect interrupt.
6. SSP transmit or receive in Slave mode (SPI/I2C).
7. USART RX or TX (Synchronous Slave mode).
8. A/D conversion (when A/D clock source is RC).
9. EEPROM write operation completion.
10. Comparator output changes state.
Other peripherals cannot generate interrupts since
during Sleep, no on-chip clocks are present.
When the SLEEP instruction is being executed, the next
instruction (PC + 1) is prefetched. For the device to
wake-up through an interrupt event, the corresponding
interrupt enable bit must be set (enabled). Wake-up is
regardless of the state of the GIE bit. If the GIE bit is
clear (disabled), the device continues execution at the
instruction after the SLEEP instruction. If the GIE bit is
set (enabled), the device executes the instruction after
the SLEEP instruction and then branches to the inter-rupt
address (0004h). In cases where the execution of
the instruction following SLEEP is not desirable, the
user should have a NOP after the SLEEP instruction.
14.14.2 WAKE-UP USING INTERRUPTS
When global interrupts are disabled (GIE cleared) and
any interrupt source has both its interrupt enable bit
and interrupt flag bit set, one of the following will occur:
• If the interrupt occurs before the execution of a
SLEEP instruction, the SLEEP instruction will
complete as a NOP. Therefore, the WDT and WDT
postscaler will not be cleared, the TO bit will not
be set and PD bits will not be cleared.
• If the interrupt occurs during or after the
execution of a SLEEP instruction, the device will
immediately wake-up from Sleep. The SLEEP
instruction will be completely executed before the
wake-up. Therefore, the WDT and WDT
postscaler will be cleared, the TO bit will be set
and the PD bit will be cleared.
Even if the flag bits were checked before executing a
SLEEP instruction, it may be possible for flag bits to
become set before the SLEEP instruction completes. To
determine whether a SLEEP instruction executed, test
the PD bit. If the PD bit is set, the SLEEP instruction
was executed as a NOP.
To ensure that the WDT is cleared, a CLRWDT
instruction should be executed before a SLEEP
instruction.

PIC16F87XA
FIGURE 14-12: WAKE-UP FROM SLEEP THROUGH INTERRUPT
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
OSC1
CLKO(4)
INT pin
INTF Flag
(INTCON<1>)
GIE bit
(INTCON<7>)
INSTRUCTION FLOW
PC
Instruction
Fetched
Instruction
Executed
Processor in
Sleep
TOST(2)
PC PC+1 PC+2
Inst(PC) = Sleep
Inst(PC - 1)
Inst(PC + 1)
Sleep
Note 1: XT, HS or LP Oscillator mode assumed.
2: TOST = 1024 TOSC (drawing not to scale). This delay will not be there for RC Oscillator mode.
3: GIE = 1 assumed. In this case, after wake- up, the processor jumps to the interrupt routine.
If GIE = 0, execution will continue in-line.
4: CLKO is not available in these oscillator modes but shown here for timing reference.
14.15 In-Circuit Debugger
When the DEBUG bit in the configuration word is pro-grammed
to a ‘0’, the in-circuit debugger functionality is
enabled. This function allows simple debugging
functions when used with MPLAB® ICD. When the
microcontroller has this feature enabled, some of the
resources are not available for general use. Table 14-8
shows which features are consumed by the
background debugger.
TABLE 14-8: DEBUGGER RESOURCES
I/O pins RB6, RB7
Stack 1 level
Program Memory Address 0000h must be NOP
Last 100h words
Data Memory 0x070 (0x0F0, 0x170, 0x1F0)
0x1EB-0x1EF
To use the in-circuit debugger function of the microcon-troller,
the design must implement In-Circuit Serial Pro-gramming
connections to MCLR/VPP, VDD, GND, RB7
and RB6. This will interface to the in-circuit debugger
module available from Microchip or one of the third
party development tool companies.
Interrupt Latency(2)
PC+2
Inst(PC + 2)
Inst(PC + 1)
PC + 2 0004h 0005h
Inst(0004h) Inst(0005h)
Dummy cycle Dummy cycle
Inst(0004h)
14.16 Program Verification/Code
Protection
If the code protection bit(s) have not been
programmed, the on-chip program memory can be
read out for verification purposes.
14.17 ID Locations
Four memory locations (2000h-2003h) are designated
as ID locations, where the user can store checksum or
other code identification numbers. These locations are
not accessible during normal execution but are
readable and writable during program/verify. It is
recommended that only the 4 Least Significant bits of
the ID location are used.

PIC16F87XA
14.18 In-Circuit Serial Programming
PIC16F87XA microcontrollers can be serially pro-grammed
while in the end application circuit. This is
simply done with two lines for clock and data and three
other lines for power, ground and the programming
voltage. This allows customers to manufacture boards
with unprogrammed devices and then program the
microcontroller just before shipping the product. This
also allows the most recent firmware or a custom
firmware to be programmed.
When using ICSP, the part must be supplied at 4.5V to
5.5V if a bulk erase will be executed. This includes
reprogramming of the code-protect, both from an on
state to an off state. For all other cases of ICSP, the part
may be programmed at the normal operating voltages.
This means calibration values, unique user IDs or user
code can be reprogrammed or added.
For complete details of serial programming, please
refer to the “PIC16F87XA Flash Memory Programming
Specification” (DS39589).
14.19 Low-Voltage (Single-Supply)
ICSP Programming
The LVP bit of the configuration word enables low-voltage
ICSP programming. This mode allows the
microcontroller to be programmed via ICSP using a
VDD source in the operating voltage range. This only
means that VPP does not have to be brought to VIHH but
can instead be left at the normal operating voltage. In
this mode, the RB3/PGM pin is dedicated to the pro-gramming
function and ceases to be a general purpose
I/O pin. During programming, VDD is applied to the
MCLR pin. To enter Programming mode, VDD must be
applied to the RB3/PGM provided the LVP bit is set.
The LVP bit defaults to on (‘1’) from the factory.
Note 1: The High-Voltage Programming mode is
always available, regardless of the state
of the LVP bit, by applying VIHH to the
MCLR pin.
2: While in Low-Voltage ICSP mode, the
RB3 pin can no longer be used as a
general purpose I/O pin.
3: When using Low-Voltage ICSP Program-ming
(LVP) and the pull-ups on PORTB
are enabled, bit 3 in the TRISB register
must be cleared to disable the pull-up on
RB3 and ensure the proper operation of
the device.
4: RB3 should not be allowed to float if LVP
is enabled. An external pull-down device
should be used to default the device to
normal operating mode. If RB3 floats
high, the PIC16F87XA device will enter
Programming mode.
5: LVP mode is enabled by default on all
devices shipped from Microchip. It can be
disabled by clearing the LVP bit in the
CONFIG register.
6: Disabling LVP will provide maximum
compatibility to other PIC16CXXX
devices.
If Low-Voltage Programming mode is not used, the LVP
bit can be programmed to a ‘0’ and RB3/PGM becomes
a digital I/O pin. However, the LVP bit may only be pro-grammed
when programming is entered with VIHH on
MCLR. The LVP bit can only be charged when using
high voltage on MCLR.
It should be noted, that once the LVP bit is programmed
to ‘0’, only the High-Voltage Programming mode is
available and only High-Voltage Programming mode
can be used to program the device.
When using low-voltage ICSP, the part must be supplied
at 4.5V to 5.5V if a bulk erase will be executed. This
includes reprogramming of the code-protect bits from an
on state to an off state. For all other cases of low-voltage
ICSP, the part may be programmed at the normal oper-ating
voltage. This means calibration values, unique
user IDs or user code can be reprogrammed or added.

PIC16F87XA
15.0 INSTRUCTION SET SUMMARY
The PIC16 instruction set is highly orthogonal and is
comprised of three basic categories:
• Byte-oriented operations
• Bit-oriented operations
• Literal and control operations
Each PIC16 instruction is a 14-bit word divided into an
opcode which specifies the instruction type and one or
more operands which further specify the operation of
the instruction. The formats for each of the categories
is presented in Figure 15-1, while the various opcode
fields are summarized in Table 15-1.
Table 15-2 lists the instructions recognized by the
MPASM™ Assembler. A complete description of each
instruction is also available in the PICmicro® Mid-Range
MCU Family Reference Manual (DS33023).
For byte-oriented instructions, ‘f’ represents a file
register designator and ‘d’ represents a destination
designator. The file register designator specifies which
file register is to be used by the instruction.
The destination designator specifies where the result of
the operation is to be placed. If ‘d’ is zero, the result is
placed in the W register. If ‘d’ is one, the result is placed
in the file register specified in the instruction.
For bit-oriented instructions, ‘b’ represents a bit field
designator which selects the bit affected by the opera-tion,
while ‘f’ represents the address of the file in which
the bit is located.
For literal and control operations, ‘k’ represents an
eight or eleven-bit constant or literal value
One instruction cycle consists of four oscillator periods;
for an oscillator frequency of 4 MHz, this gives a normal
instruction execution time of 1 μs. All instructions are
executed within a single instruction cycle, unless a
conditional test is true, or the program counter is
changed as a result of an instruction. When this occurs,
the execution takes two instruction cycles with the
second cycle executed as a NOP.
Note: To maintain upward compatibility with
future PIC16F87XA products, do not use
the OPTION and TRIS instructions.
All instruction examples use the format ‘0xhh’ to
represent a hexadecimal number, where ‘h’ signifies a
hexadecimal digit.
15.1 READ-MODIFY-WRITE
OPERATIONS
Any instruction that specifies a file register as part of
the instruction performs a Read-Modify-Write (R-M-W)
operation. The register is read, the data is modified,
and the result is stored according to either the instruc-tion
or the destination designator ‘d’. A read operation
is performed on a register even if the instruction writes
to that register.
For example, a “CLRF PORTB” instruction will read
PORTB, clear all the data bits, then write the result
back to PORTB. This example would have the unin-tended
result that the condition that sets the RBIF flag
would be cleared.
TABLE 15-1: OPCODE FIELD
DESCRIPTIONS
Field Description
f Register file address (0x00 to 0x7F)
W Working register (accumulator)
b Bit address within an 8-bit file register
k Literal field, constant data or label
x Don't care location (= 0 or 1).
The assembler will generate code with x = 0.
It is the recommended form of use for
compatibility with all Microchip software tools.
d Destination select; d = 0: store result in W,
d = 1: store result in file register f.
Default is d = 1.
PC Program Counter
TO Time-out bit
PD Power-down bit
FIGURE 15-1: GENERAL FORMAT FOR
INSTRUCTIONS
Byte-oriented file register operations
13 8 7 6 0
OPCODE d f (FILE #)
d = 0 for destination W
d = 1 for destination f
f = 7-bit file register address
Bit-oriented file register operations
13 10 9 7 6 0
OPCODE b (BIT #) f (FILE #)
b = 3-bit bit address
f = 7-bit file register address
Literal and control operations
General
13 8 7 0
OPCODE k (literal)
k = 8-bit immediate value
CALL and GOTO instructions only
13 11 10 0
OPCODE k (literal)
k = 11-bit immediate value

PIC16F87XA
TABLE 15-2: PIC16F87XA INSTRUCTION SET
Mnemonic,
Operands
Description Cycles
14-Bit Opcode Status
Affected
Notes
MSb LSb
BYTE-ORIENTED FILE REGISTER OPERATIONS
ADDWF
ANDWF
CLRF
CLRW
COMF
DECF
DECFSZ
INCF
INCFSZ
IORWF
MOVF
MOVWF
NOP
RLF
RRF
SUBWF
SWAPF
XORWF
f, d
f, d
f
-
f, d
f, d
f, d
f, d
f, d
f, d
f, d
f
-
f, d
f, d
f, d
f, d
f, d
Add W and f
AND W with f
Clear f
Clear W
Complement f
Decrement f
Decrement f, Skip if 0
Increment f
Increment f, Skip if 0
Inclusive OR W with f
Move f
Move W to f
No Operation
Rotate Left f through Carry
Rotate Right f through Carry
Subtract W from f
Swap nibbles in f
Exclusive OR W with f
1
1
1
1
1
1
1(2)
1
1(2)
1
1
1
1
1
1
1
1
1
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
00
0111
0101
0001
0001
1001
0011
1011
1010
1111
0100
1000
0000
0000
1101
1100
0010
1110
0110
dfff
dfff
lfff
0xxx
dfff
dfff
dfff
dfff
dfff
dfff
dfff
lfff
0xx0
dfff
dfff
dfff
dfff
dfff
ffff
ffff
ffff
xxxx
ffff
ffff
ffff
ffff
ffff
ffff
ffff
ffff
0000
ffff
ffff
ffff
ffff
ffff
C,DC,Z
Z
Z
Z
Z
Z
Z
Z
Z
C
C
C,DC,Z
Z
1,2
1,2
2
1,2
1,2
1,2,3
1,2
1,2,3
1,2
1,2
1,2
1,2
1,2
1,2
1,2
BIT-ORIENTED FILE REGISTER OPERATIONS
BCF
BSF
BTFSC
BTFSS
f, b
f, b
f, b
f, b
Bit Clear f
Bit Set f
Bit Test f, Skip if Clear
Bit Test f, Skip if Set
1
1
1 (2)
1 (2)
01
01
01
01
00bb
01bb
10bb
11bb
bfff
bfff
bfff
bfff
ffff
ffff
ffff
ffff
1,2
1,2
3
3
LITERAL AND CONTROL OPERATIONS
ADDLW
ANDLW
CALL
CLRWDT
GOTO
IORLW
MOVLW
RETFIE
RETLW
RETURN
SLEEP
SUBLW
XORLW
k
k
k
-
k
k
k
-
k
-
-
k
k
Add Literal and W
AND Literal with W
Call Subroutine
Clear Watchdog Timer
Go to Address
Inclusive OR Literal with W
Move Literal to W
Return from Interrupt
Return with Literal in W
Return from Subroutine
Go into Standby mode
Subtract W from Literal
Exclusive OR Literal with W
1
1
2
1
2
1
1
2
2
2
1
1
1
11
11
10
00
10
11
11
00
11
00
00
11
11
111x
1001
0kkk
0000
1kkk
1000
00xx
0000
01xx
0000
0000
110x
1010
kkkk
kkkk
kkkk
0110
kkkk
kkkk
kkkk
0000
kkkk
0000
0110
kkkk
kkkk
kkkk
kkkk
kkkk
0100
kkkk
kkkk
kkkk
1001
kkkk
1000
0011
kkkk
kkkk
C,DC,Z
Z
TO,PD
Z
TO,PD
C,DC,Z
Z
Note 1: When an I/O register is modified as a function of itself ( e.g., MOVF PORTB, 1), the value used will be that value present
on the pins themselves. For example, if the data latch is ‘1’ for a pin configured as input and is driven low by an external
device, the data will be written back with a ‘0’.
2: If this instruction is executed on the TMR0 register (and where applicable, d = 1), the prescaler will be cleared if
assigned to the Timer0 module.
3: If Program Counter (PC) is modified, or a conditional test is true, the instruction requires two cycles. The second cycle is
executed as a NOP.
Note: Additional information on the mid-range instruction set is available in the PICmicro® Mid-Range MCU
Family Reference Manual (DS33023).

PIC16F87XA
15.2 Instruction Descriptions
ADDLW Add Literal and W
Syntax: [ label ] ADDLW k
Operands: 0 ≤ k ≤ 255
Operation: (W) + k → (W)
Status Affected: C, DC, Z
Description: The contents of the W register
are added to the eight-bit literal ‘k’
and the result is placed in the W
register.
ADDWF Add W and f
Syntax: [ label ] ADDWF f,d
Operands: 0 ≤ f ≤ 127
d ∈ [0,1]
Operation: (W) + (f) → (destination)
Description: Add the contents of the W register
with register ‘f’. If ‘d’ is ‘0’, the
result is stored in the W register. If
‘d’ is ‘1’, the result is stored back
in register ‘f’.
ANDLW AND Literal with W
Syntax: [ label ] ANDLW k
Operation: (W) .AND. (k) → (W)
Status Affected: Z
Description: The contents of W register are
AND’ed with the eight-bit literal
‘k’. The result is placed in the W
register.
ANDWF AND W with f
Syntax: [ label ] ANDWF f,d
d ∈ [0,1]
Operation: (W) .AND. (f) → (destination)
Status Affected: Z
Description: AND the W register with register
‘f’. If ‘d’ is ‘0’, the result is stored in
the W register. If ‘d’ is ‘1’, the
result is stored back in register ‘f’.
BCF Bit Clear f
Syntax: [ label ] BCF f,b
0 ≤ b ≤ 7
Operation: 0 → (f<b>)
Status Affected: None
Description: Bit ‘b’ in register ‘f’ is cleared.
BSF Bit Set f
Syntax: [ label ] BSF f,b
0 ≤ b ≤ 7
Operation: 1 → (f<b>)
Description: Bit ‘b’ in register ‘f’ is set.
BTFSS Bit Test f, Skip if Set
Syntax: [ label ] BTFSS f,b
0 ≤ b < 7
Operation: skip if (f<b>) = 1
Description: If bit ‘b’ in register ‘f’ is ‘0’, the next
instruction is executed.
If bit ‘b’ is ‘1’, then the next instruc-tion
is discarded and a NOP is
executed instead, making this a
2 TCY instruction.
BTFSC Bit Test, Skip if Clear
Syntax: [ label ] BTFSC f,b
0 ≤ b ≤ 7
Operation: skip if (f<b>) = 0
Description: If bit ‘b’ in register ‘f’ is ‘1’, the next
instruction is executed.
If bit ‘b’ in register ‘f’ is ‘0’, the next
instruction is discarded and a NOP
is executed instead, making this a
2 TCY instruction.

PIC16F87XA
CALL Call Subroutine
Syntax: [ label ] CALL k
Operation: (PC)+ 1→ TOS,
k → PC<10:0>,
(PCLATH<4:3>) → PC<12:11>
Description: Call Subroutine. First, return
address (PC+1) is pushed onto
the stack. The eleven-bit
immediate address is loaded into
PC bits <10:0>. The upper bits of
the PC are loaded from PCLATH.
CALL is a two-cycle instruction.
CLRF Clear f
Syntax: [ label ] CLRF f
Operation: 00h → (f)
1 → Z
Status Affected: Z
Description: The contents of register ‘f’ are
cleared and the Z bit is set.
CLRW Clear W
Syntax: [ label ] CLRW
Operands: None
Operation: 00h → (W)
1 → Z
Status Affected: Z
Description: W register is cleared. Zero bit (Z)
is set.
CLRWDT Clear Watchdog Timer
Syntax: [ label ] CLRWDT
Operands: None
Operation: 00h → WDT
0 → WDT prescaler,
1 → TO
1 → PD
Status Affected: TO, PD
Description: CLRWDT instruction resets the
Watchdog Timer. It also resets the
prescaler of the WDT. Status bits,
TO and PD, are set.
COMF Complement f
Syntax: [ label ] COMF f,d
d ∈ [0,1]
Operation: (f) → (destination)
Status Affected: Z
complemented. If ‘d’ is ‘0’, the
result is stored in W. If ‘d’ is ‘1’,
the result is stored back in
register ‘f’.
DECF Decrement f
Syntax: [ label ] DECF f,d
d ∈ [0,1]
Operation: (f) - 1 → (destination)
Status Affected: Z
Description: Decrement register ‘f’. If ‘d’ is ‘0’,
the result is stored in the W
register. If ‘d’ is ‘1’, the result is
stored back in register ‘f’.

PIC16F87XA
DECFSZ Decrement f, Skip if 0
Syntax: [ label ] DECFSZ f,d
d ∈ [0,1]
Operation: (f) - 1 → (destination);
skip if result = 0
decremented. If ‘d’ is ‘0’, the result
is placed in the W register. If ‘d’ is
‘1’, the result is placed back in
register ‘f’.
If the result is ‘1’, the next instruc-tion
is executed. If the result is ‘0’,
then a NOP is executed instead,
making it a 2 TCY instruction.
GOTO Unconditional Branch
Syntax: [ label ] GOTO k
Operation: k → PC<10:0>
PCLATH<4:3> → PC<12:11>
Description: GOTO is an unconditional branch.
The eleven-bit immediate value is
loaded into PC bits <10:0>. The
upper bits of PC are loaded from
PCLATH<4:3>. GOTO is a
two-cycle instruction.
INCF Increment f
Syntax: [ label ] INCF f,d
d ∈ [0,1]
Operation: (f) + 1 → (destination)
Status Affected: Z
incremented. If ‘d’ is ‘0’, the result
register ‘f’.
INCFSZ Increment f, Skip if 0
Syntax: [ label ] INCFSZ f,d
d ∈ [0,1]
Operation: (f) + 1 → (destination),
skip if result = 0
incremented. If ‘d’ is ‘0’, the result
register ‘f’.
If the result is ‘1’, the next instruc-tion
is executed. If the result is ‘0’,
a NOP is executed instead, making
it a 2 TCY instruction.
IORLW Inclusive OR Literal with W
Syntax: [ label ] IORLW k
Operation: (W) .OR. k → (W)
Status Affected: Z
Description: The contents of the W register are
OR’ed with the eight-bit literal ‘k’.
The result is placed in the W
register.
IORWF Inclusive OR W with f
Syntax: [ label ] IORWF f,d
d ∈ [0,1]
Operation: (W) .OR. (f) → (destination)
Status Affected: Z
Description: Inclusive OR the W register with
register ‘f’. If ‘d’ is ‘0’, the result is
placed in the W register. If ‘d’ is
register ‘f’.

PIC16F87XA
RLF Rotate Left f through Carry
Syntax: [ label ] RLF f,d
d ∈ [0,1]
Operation: See description below
Status Affected: C
rotated one bit to the left through the
Carry flag. If ‘d’ is ‘0’, the result is
placed in the W register. If ‘d’ is ‘1’,
the result is stored back in register ‘f’.
C Register f
RETURN Return from Subroutine
Syntax: [ label ] RETURN
Operands: None
Operation: TOS → PC
Description: Return from subroutine. The stack
is POPed and the top of the stack
(TOS) is loaded into the program
counter. This is a two-cycle
instruction.
RRF Rotate Right f through Carry
Syntax: [ label ] RRF f,d
d ∈ [0,1]
Operation: See description below
Status Affected: C
rotated one bit to the right through
the Carry flag. If ‘d’ is ‘0’, the
result is placed in the W register.
If ‘d’ is ‘1’, the result is placed
back in register ‘f’.
C Register f
SLEEP
Syntax: [ label ] SLEEP
Operands: None
Operation: 00h → WDT,
0 → WDT prescaler,
1 → TO,
0 → PD
Status Affected: TO, PD
Description: The power-down status bit, PD,
is cleared. Time-out status bit,
TO, is set. Watchdog Timer and
its prescaler are cleared.
The processor is put into Sleep
mode with the oscillator stopped.
SUBLW Subtract W from Literal
Syntax: [ label ] SUBLW k
Operation: k - (W) → (W)
Description: The W register is subtracted (2’s
complement method) from the
eight-bit literal ‘k’. The result is
placed in the W register.
SUBWF Subtract W from f
Syntax: [ label ] SUBWF f,d
d ∈ [0,1]
Operation: (f) - (W) → (destination)
Status
C, DC, Z
Affected:
Description: Subtract (2’s complement method)
W register from register ‘f’. If ‘d’ is
‘0’, the result is stored in the W

PIC16F87XA
SWAPF Swap Nibbles in f
Syntax: [ label ] SWAPF f,d
d ∈ [0,1]
Operation: (f<3:0>) → (destination<7:4>),
(f<7:4>) → (destination<3:0>)
Description: The upper and lower nibbles of
register ‘f’ are exchanged. If ‘d’ is
‘0’, the result is placed in the W
placed in register ‘f’.
XORLW Exclusive OR Literal with W
Syntax: [ label ] XORLW k
Operation: (W) .XOR. k → (W)
Status Affected: Z
Description: The contents of the W register
are XOR’ed with the eight-bit
literal ‘k’. The result is placed in
the W register.
XORWF Exclusive OR W with f
Syntax: [ label ] XORWF f,d
d ∈ [0,1]
Operation: (W) .XOR. (f) → (destination)
Status Affected: Z
Description: Exclusive OR the contents of the
W register with register ‘f’. If ‘d’ is
‘0’, the result is stored in the W

PIC16F87XA
NOTES:

PIC16F87XA
16.0 DEVELOPMENT SUPPORT
The PICmicro® microcontrollers are supported with a
full range of hardware and software development tools:
• Integrated Development Environment
- MPLAB® IDE Software
• Assemblers/Compilers/Linkers
- MPASMTM Assembler
- MPLAB C17 and MPLAB C18 C Compilers
- MPLINKTM Object Linker/
MPLIBTM Object Librarian
- MPLAB C30 C Compiler
- MPLAB ASM30 Assembler/Linker/Library
• Simulators
- MPLAB SIM Software Simulator
- MPLAB dsPIC30 Software Simulator
• Emulators
- MPLAB ICE 2000 In-Circuit Emulator
- MPLAB ICE 4000 In-Circuit Emulator
• In-Circuit Debugger
- MPLAB ICD 2
• Device Programmers
- PRO MATE® II Universal Device Programmer
- PICSTART® Plus Development Programmer
• Low Cost Demonstration Boards
- PICDEMTM 1 Demonstration Board
- PICDEM.netTM Demonstration Board
- PICDEM 2 Plus Demonstration Board
- PICDEM 3 Demonstration Board
- PICDEM 18R Demonstration Board
- PICDEM LIN Demonstration Board
- PICDEM USB Demonstration Board
• Evaluation Kits
- KEELOQ®
- PICDEM MSC
- microID®
- CAN
- PowerSmart®
- Analog
16.1 MPLAB Integrated Development
Environment Software
The MPLAB IDE software brings an ease of software
development previously unseen in the 8/16-bit micro-controller
market. The MPLAB IDE is a Windows®
based application that contains:
• An interface to debugging tools
- simulator
- programmer (sold separately)
- emulator (sold separately)
- in-circuit debugger (sold separately)
• A full-featured editor with color coded context
• A multiple project manager
• Customizable data windows with direct edit of
contents
• High level source code debugging
• Mouse over variable inspection
• Extensive on-line help
The MPLAB IDE allows you to:
• Edit your source files (either assembly or C)
• One touch assemble (or compile) and download
to PICmicro emulator and simulator tools
(automatically updates all project information)
• Debug using:
- source files (assembly or C)
- absolute listing file (mixed assembly and C)
- machine code
MPLAB IDE supports multiple debugging tools in a
single development paradigm, from the cost effective
simulators, through low cost in-circuit debuggers, to
full-featured emulators. This eliminates the learning
curve when upgrading to tools with increasing flexibility
and power.
16.2 MPASM Assembler
The MPASM assembler is a full-featured, universal
macro assembler for all PICmicro MCUs.
The MPASM assembler generates relocatable object
files for the MPLINK object linker, Intel® standard HEX
files, MAP files to detail memory usage and symbol ref-erence,
absolute LST files that contain source lines and
generated machine code and COFF files for
debugging.
The MPASM assembler features include:
• Integration into MPLAB IDE projects
• User defined macros to streamline assembly code
• Conditional assembly for multi-purpose source
files
• Directives that allow complete control over the
assembly process
 2003 Microchip Technology Inc. DS39582B-page167

PIC16F87XA
16.3 MPLAB C17 and MPLAB C18
C Compilers
The MPLAB C17 and MPLAB C18 Code Development
Systems are complete ANSI C compilers for
Microchip’s PIC17CXXX and PIC18CXXX family of
microcontrollers. These compilers provide powerful
integration capabilities, superior code optimization and
ease of use not found with other compilers.
For easy source level debugging, the compilers provide
symbol information that is optimized to the MPLAB IDE
debugger.
16.4 MPLINK Object Linker/
MPLIB Object Librarian
The MPLINK object linker combines relocatable
objects created by the MPASM assembler and the
MPLAB C17 and MPLAB C18 C compilers. It can link
relocatable objects from precompiled libraries, using
directives from a linker script.
The MPLIB object librarian manages the creation and
modification of library files of pre-compiled code. When
a routine from a library is called from a source file, only
the modules that contain that routine will be linked in
with the application. This allows large libraries to be
used efficiently in many different applications.
The object linker/library features include:
• Efficient linking of single libraries instead of many
smaller files
• Enhanced code maintainability by grouping
related modules together
• Flexible creation of libraries with easy module
listing, replacement, deletion and extraction
16.5 MPLAB C30 C Compiler
The MPLAB C30 C compiler is a full-featured, ANSI
compliant, optimizing compiler that translates standard
ANSI C programs into dsPIC30F assembly language
source. The compiler also supports many command-line
options and language extensions to take full
advantage of the dsPIC30F device hardware capabili-ties,
and afford fine control of the compiler code
generator.
MPLAB C30 is distributed with a complete ANSI C
standard library. All library functions have been vali-dated
and conform to the ANSI C library standard. The
library includes functions for string manipulation,
dynamic memory allocation, data conversion, time-keeping,
and math functions (trigonometric, exponen-tial
and hyperbolic). The compiler provides symbolic
information for high level source debugging with the
MPLAB IDE.
16.6 MPLAB ASM30 Assembler, Linker,
and Librarian
MPLAB ASM30 assembler produces relocatable
machine code from symbolic assembly language for
dsPIC30F devices. MPLAB C30 compiler uses the
assembler to produce it’s object file. The assembler
generates relocatable object files that can then be
archived or linked with other relocatable object files and
archives to create an executable file. Notable features
of the assembler include:
• Support for the entire dsPIC30F instruction set
• Support for fixed-point and floating-point data
• Command line interface
• Rich directive set
• Flexible macro language
• MPLAB IDE compatibility
16.7 MPLAB SIM Software Simulator
The MPLAB SIM software simulator allows code devel-opment
in a PC hosted environment by simulating the
PICmicro series microcontrollers on an instruction
level. On any given instruction, the data areas can be
examined or modified and stimuli can be applied from
a file, or user defined key press, to any pin. The execu-tion
can be performed in Single-Step, Execute Until
Break, or Trace mode.
The MPLAB SIM simulator fully supports symbolic
debugging using the MPLAB C17 and MPLAB C18
C Compilers, as well as the MPASM assembler. The
software simulator offers the flexibility to develop and
debug code outside of the laboratory environment,
making it an excellent, economical software
development tool.
16.8 MPLAB SIM30 Software Simulator
The MPLAB SIM30 software simulator allows code
development in a PC hosted environment by simulating
the dsPIC30F series microcontrollers on an instruction
level. On any given instruction, the data areas can be
examined or modified and stimuli can be applied from
a file, or user defined key press, to any of the pins.
The MPLAB SIM30 simulator fully supports symbolic
debugging using the MPLAB C30 C Compiler and
MPLAB ASM30 assembler. The simulator runs in either
a Command Line mode for automated tasks, or from
MPLAB IDE. This high speed simulator is designed to
debug, analyze and optimize time intensive DSP
routines.
DS39582B-page 168  2003 Microchip Technology Inc.

PIC16F87XA
16.9 MPLAB ICE 2000
High Performance Universal
In-Circuit Emulator
The MPLAB ICE 2000 universal in-circuit emulator is
intended to provide the product development engineer
with a complete microcontroller design tool set for
PICmicro microcontrollers. Software control of the
MPLAB ICE 2000 in-circuit emulator is advanced by
the MPLAB Integrated Development Environment,
which allows editing, building, downloading and source
debugging from a single environment.
The MPLAB ICE 2000 is a full-featured emulator sys-tem
with enhanced trace, trigger and data monitoring
features. Interchangeable processor modules allow the
system to be easily reconfigured for emulation of differ-ent
processors. The universal architecture of the
MPLAB ICE in-circuit emulator allows expansion to
support new PICmicro microcontrollers.
The MPLAB ICE 2000 in-circuit emulator system has
been designed as a real-time emulation system with
advanced features that are typically found on more
expensive development tools. The PC platform and
Microsoft® Windows 32-bit operating system were
chosen to best make these features available in a
simple, unified application.
16.10 MPLAB ICE 4000
High Performance Universal
In-Circuit Emulator
The MPLAB ICE 4000 universal in-circuit emulator is
intended to provide the product development engineer
with a complete microcontroller design tool set for high-end
PICmicro microcontrollers. Software control of the
MPLAB ICE in-circuit emulator is provided by the
MPLAB Integrated Development Environment, which
allows editing, building, downloading and source
debugging from a single environment.
The MPLAB ICD 4000 is a premium emulator system,
providing the features of MPLAB ICE 2000, but with
increased emulation memory and high speed perfor-mance
for dsPIC30F and PIC18XXXX devices. Its
advanced emulator features include complex triggering
and timing, up to 2 Mb of emulation memory, and the
ability to view variables in real-time.
The MPLAB ICE 4000 in-circuit emulator system has
been designed as a real-time emulation system with
advanced features that are typically found on more
expensive development tools. The PC platform and
Microsoft Windows 32-bit operating system were cho-sen
to best make these features available in a simple,
unified application.
16.11 MPLAB ICD 2 In-Circuit Debugger
Microchip’s In-Circuit Debugger, MPLAB ICD 2, is a
powerful, low-cost, run-time development tool,
connecting to the host PC via an RS-232 or high-speed
USB interface. This tool is based on the Flash
PICmicro MCUs and can be used to develop for these
and other PICmicro microcontrollers. The MPLAB
ICD 2 utilizes the in-circuit debugging capability built
into the Flash devices. This feature, along with
Microchip’s In-Circuit Serial ProgrammingTM (ICSPTM)
protocol, offers cost effective in-circuit Flash debugging
from the graphical user interface of the MPLAB Inte-grated
Development Environment. This enables a
designer to develop and debug source code by setting
breakpoints, single-stepping and watching variables,
CPU status and peripheral registers. Running at full
speed enables testing hardware and applications in
real-time. MPLAB ICD 2 also serves as a development
programmer for selected PICmicro devices.
16.12 PRO MATE II Universal Device
Programmer
The PRO MATE II is a universal, CE compliant device
programmer with programmable voltage verification at
VDDMIN and VDDMAX for maximum reliability. It features
an LCD display for instructions and error messages
and a modular detachable socket assembly to support
various package types. In Stand-Alone mode, the
PRO MATE II device programmer can read, verify, and
program PICmicro devices without a PC connection. It
can also set code protection in this mode.
16.13 PICSTART Plus Development
Programmer
The PICSTART Plus development programmer is an
easy-to-use, low-cost, prototype programmer. It con-nects
to the PC via a COM (RS-232) port. MPLAB
Integrated Development Environment software makes
using the programmer simple and efficient. The
PICSTART Plus development programmer supports
most PICmicro devices up to 40 pins. Larger pin count
devices, such as the PIC16C92X and PIC17C76X,
may be supported with an adapter socket. The
PICSTART Plus development programmer is CE
compliant.

PIC16F87XA
16.14 PICDEM 1 PICmicro
Demonstration Board
The PICDEM 1 demonstration board demonstrates the
capabilities of the PIC16C5X (PIC16C54 to
PIC16C58A), PIC16C61, PIC16C62X, PIC16C71,
PIC16C8X, PIC17C42, PIC17C43 and PIC17C44. All
necessary hardware and software is included to run
basic demo programs. The sample microcontrollers
provided with the PICDEM 1 demonstration board can
be programmed with a PRO MATE II device program-mer,
or a PICSTART Plus development programmer.
The PICDEM 1 demonstration board can be connected
to the MPLAB ICE in-circuit emulator for testing. A pro-totype
area extends the circuitry for additional applica-tion
components. Features include an RS-232
interface, a potentiometer for simulated analog input,
push button switches and eight LEDs.
16.15 PICDEM.net Internet/Ethernet
Demonstration Board
The PICDEM.net demonstration board is an Internet/
Ethernet demonstration board using the PIC18F452
microcontroller and TCP/IP firmware. The board
supports any 40-pin DIP device that conforms to the
standard pinout used by the PIC16F877 or
PIC18C452. This kit features a user friendly TCP/IP
stack, web server with HTML, a 24L256 Serial
EEPROM for Xmodem download to web pages into
Serial EEPROM, ICSP/MPLAB ICD 2 interface con-nector,
an Ethernet interface, RS-232 interface, and a
16 x 2 LCD display. Also included is the book and
CD-ROM “TCP/IP Lean, Web Servers for Embedded
Systems,” by Jeremy Bentham.
16.16 PICDEM 2 Plus
Demonstration Board
The PICDEM 2 Plus demonstration board supports
many 18-, 28-, and 40-pin microcontrollers, including
PIC16F87X and PIC18FXX2 devices. All the neces-sary
hardware and software is included to run the dem-onstration
programs. The sample microcontrollers
provided with the PICDEM 2 demonstration board can
be programmed with a PRO MATE II device program-mer,
PICSTART Plus development programmer, or
MPLAB ICD 2 with a Universal Programmer Adapter.
The MPLAB ICD 2 and MPLAB ICE in-circuit emulators
may also be used with the PICDEM 2 demonstration
board to test firmware. A prototype area extends the
circuitry for additional application components. Some
of the features include an RS-232 interface, a 2 x 16
LCD display, a piezo speaker, an on-board temperature
sensor, four LEDs, and sample PIC18F452 and
PIC16F877 Flash microcontrollers.
16.17 PICDEM 3 PIC16C92X
Demonstration Board
The PICDEM 3 demonstration board supports the
PIC16C923 and PIC16C924 in the PLCC package. All
the necessary hardware and software is included to run
the demonstration programs.
16.18 PICDEM 4 8/14/18-Pin
Demonstration Board
The PICDEM 4 can be used to demonstrate the capa-bilities
of the 8, 14, and 18-pin PIC16XXXX and
PIC18XXXX MCUs, including the PIC16F818/819,
PIC16F87/88, PIC16F62XA and the PIC18F1320 fam-ily
of microcontrollers. PICDEM 4 is intended to show-case
the many features of these low pin count parts,
including LIN and Motor Control using ECCP. Special
provisions are made for low power operation with the
supercapacitor circuit, and jumpers allow on-board
hardware to be disabled to eliminate current draw in
this mode. Included on the demo board are provisions
for Crystal, RC or Canned Oscillator modes, a five volt
regulator for use with a nine volt wall adapter or battery,
DB-9 RS-232 interface, ICD connector for program-ming
via ICSP and development with MPLAB ICD 2,
2x16 liquid crystal display, PCB footprints for H-Bridge
motor driver, LIN transceiver and EEPROM. Also
included are: header for expansion, eight LEDs, four
potentiometers, three push buttons and a prototyping
area. Included with the kit is a PIC16F627A and a
PIC18F1320. Tutorial firmware is included along with
the User’s Guide.
16.19 PICDEM 17 Demonstration Board
The PICDEM 17 demonstration board is an evaluation
board that demonstrates the capabilities of several
Microchip microcontrollers, including PIC17C752,
PIC17C756A, PIC17C762 and PIC17C766. A pro-grammed
sample is included. The PRO MATE II device
programmer, or the PICSTART Plus development pro-grammer,
can be used to reprogram the device for user
tailored application development. The PICDEM 17
demonstration board supports program download and
execution from external on-board Flash memory. A
generous prototype area is available for user hardware
expansion.

PIC16F87XA
16.20 PICDEM 18R PIC18C601/801
Demonstration Board
The PICDEM 18R demonstration board serves to assist
development of the PIC18C601/801 family of Microchip
microcontrollers. It provides hardware implementation
of both 8-bit Multiplexed/Demultiplexed and 16-bit
Memory modes. The board includes 2 Mb external
Flash memory and 128 Kb SRAM memory, as well as
serial EEPROM, allowing access to the wide range of
memory types supported by the PIC18C601/801.
16.21 PICDEM LIN PIC16C43X
Demonstration Board
The powerful LIN hardware and software kit includes a
series of boards and three PICmicro microcontrollers.
The small footprint PIC16C432 and PIC16C433 are
used as slaves in the LIN communication and feature
on-board LIN transceivers. A PIC16F874 Flash micro-controller
serves as the master. All three microcontrol-lers
are programmed with firmware to provide LIN bus
communication.
16.22 PICkitTM 1 Flash Starter Kit
A complete “development system in a box”, the PICkit
Flash Starter Kit includes a convenient multi-section
board for programming, evaluation and development of
8/14-pin Flash PIC® microcontrollers. Powered via
USB, the board operates under a simple Windows GUI.
The PICkit 1 Starter Kit includes the user's guide (on
CD ROM), PICkit 1 tutorial software and code for vari-ous
applications. Also included are MPLAB® IDE (Inte-grated
Development Environment) software, software
and hardware “Tips 'n Tricks for 8-pin Flash PIC®
Microcontrollers” Handbook and a USB Interface
Cable. Supports all current 8/14-pin Flash PIC
microcontrollers, as well as many future planned
devices.
16.23 PICDEM USB PIC16C7X5
Demonstration Board
The PICDEM USB Demonstration Board shows off the
capabilities of the PIC16C745 and PIC16C765 USB
microcontrollers. This board provides the basis for
future USB products.
16.24 Evaluation and
Programming Tools
In addition to the PICDEM series of circuits, Microchip
has a line of evaluation kits and demonstration software
for these products.
• KEELOQ evaluation and programming tools for
Microchip’s HCS Secure Data Products
• CAN developers kit for automotive network
applications
• Analog design boards and filter design software
• PowerSmart battery charging evaluation/
calibration kits
• IrDA® development kit
• microID development and rfLabTM development
software
• SEEVAL® designer kit for memory evaluation and
endurance calculations
• PICDEM MSC demo boards for Switching mode
power supply, high power IR driver, delta sigma
ADC, and flow rate sensor
Check the Microchip web page and the latest Product
Line Card for the complete list of demonstration and
evaluation kits.

PIC16F87XA
NOTES:

PIC16F87XA
17.0 ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings †
Ambient temperature under bias................................................................................................................ .-55 to +125°C
Storage temperature .............................................................................................................................. -65°C to +150°C
Voltage on any pin with respect to VSS (except VDD, MCLR. and RA4) ......................................... -0.3V to (VDD + 0.3V)
Voltage on VDD with respect to VSS ............................................................................................................ -0.3 to +7.5V
Voltage on MCLR with respect to VSS (Note 2) .................................................................................................0 to +14V
Voltage on RA4 with respect to Vss ..................................................................................................................0 to +8.5V
Total power dissipation (Note 1) ...............................................................................................................................1.0W
Maximum current out of VSS pin ...........................................................................................................................300 mA
Maximum current into VDD pin ..............................................................................................................................250 mA
Input clamp current, IIK (VI < 0 or VI > VDD)..................................................................................................................... ± 20 mA
Output clamp current, IOK (VO < 0 or VO > VDD) ............................................................................................................. ± 20 mA
Maximum output current sunk by any I/O pin..........................................................................................................25 mA
Maximum output current sourced by any I/O pin ....................................................................................................25 mA
Maximum current sunk by PORTA, PORTB and PORTE (combined) (Note 3)....................................................200 mA
Maximum current sourced by PORTA, PORTB and PORTE (combined) (Note 3)...............................................200 mA
Maximum current sunk by PORTC and PORTD (combined) (Note 3) .................................................................200 mA
Maximum current sourced by PORTC and PORTD (combined) (Note 3) ............................................................200 mA
Note 1: Power dissipation is calculated as follows: Pdis = VDD x {IDD - Σ IOH} + Σ {(VDD - VOH) x IOH} + Σ(VOl x IOL)
2: Voltage spikes below VSS at the MCLR pin, inducing currents greater than 80 mA, may cause latch-up.
Thus, a series resistor of 50-100Ω should be used when applying a “low” level to the MCLR pin rather than
pulling this pin directly to VSS.
3: PORTD and PORTE are not implemented on PIC16F873A/876A devices.
† NOTICE: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the
device. This is a stress rating only and functional operation of the device at those or any other conditions above those
indicated in the operation listings of this specification is not implied. Exposure to maximum rating conditions for
extended periods may affect device reliability.

PIC16F87XA
FIGURE 17-1: PIC16F87XA VOLTAGE-FREQUENCY GRAPH (INDUSTRIAL, EXTENDED)
PIC16F87XA
Frequency
Voltage
6.0V
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
2.0V
20 MHz
FIGURE 17-2: PIC16LF87XA VOLTAGE-FREQUENCY GRAPH (INDUSTRIAL)
PIC16LF87XA
4 MHz 10 MHz
Frequency
Voltage
6.0V
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
2.0V
FMAX = (6.0 MHz/V) (VDDAPPMIN – 2.0V) + 4 MHz
Note 1: VDDAPPMIN is the minimum voltage of the PICmicro® device in the application.
Note 2: FMAX has a maximum frequency of 10 MHz.

PIC16F87XA
17.1 DC Characteristics: PIC16F873A/874A/876A/877A (Industrial, Extended)
PIC16LF873A/874A/876A/877A (Industrial)
PIC16LF873A/874A/876A/877A
(Industrial)
Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C ≤ TA ≤ +85°C for industrial
PIC16F873A/874A/876A/877A
(Industrial, Extended)
-40°C ≤ TA ≤ +125°C for extended
Param
No.
Symbol
Characteristic/
Device
Min Typ† Max Units Conditions
VDD Supply Voltage
D001 16LF87XA 2.0 — 5.5 V All configurations
(DC to 10 MHz)
D001 16F87XA 4.0 — 5.5 V All configurations
D001A VBOR 5.5 V BOR enabled, FMAX = 14 MHz(7)
D002 VDR RAM Data Retention
Voltage(1)
— 1.5 — V
D003 VPOR VDD Start Voltage to
ensure internal Power-on
Reset signal
— VSS — V See Section 14.5 “Power-on
Reset (POR)” for details
D004 SVDD VDD Rise Rate to ensure
internal Power-on Reset
signal
0.05 — — V/ms See Section 14.5 “Power-on
Reset (POR)” for details
D005 VBOR Brown-out Reset
Voltage
3.65 4.0 4.35 V BODEN bit in configuration word
enabled
Legend: Rows with standard voltage device data only are shaded for improved readability.
† Data in “Typ” column is at 5V, 25°C, unless otherwise stated. These parameters are for design guidance
only and are not tested.
Note 1: This is the limit to which VDD can be lowered without losing RAM data.
2: The supply current is mainly a function of the operating voltage and frequency. Other factors, such as I/O
pin loading, switching rate, oscillator type, internal code execution pattern and temperature, also have an
impact on the current consumption.
The test conditions for all IDD measurements in active operation mode are:
OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD;
MCLR = VDD; WDT enabled/disabled as specified.
3: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is
measured with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD and VSS.
4: For RC osc configuration, current through REXT is not included. The current through the resistor can be
estimated by the formula Ir = VDD/2REXT (mA) with REXT in kΩ.
5: Timer1 oscillator (when enabled) adds approximately 20 μA to the specification. This value is from
characterization and is for design guidance only. This is not tested.
6: The Δ current is the additional current consumed when this peripheral is enabled. This current should be
added to the base IDD or IPD measurement.
7: When BOR is enabled, the device will operate correctly until the VBOR voltage trip point is reached.

PIC16F87XA
PIC16LF873A/874A/876A/877A (Industrial) (Continued)
PIC16LF873A/874A/876A/877A
(Industrial)
PIC16F873A/874A/876A/877A
Symbol
Characteristic/
Device
IDD Supply Current(2,5)
Param
No.
D010 16LF87XA — 0.6 2.0 mA XT, RC osc configurations,
FOSC = 4 MHz, VDD = 3.0V
D010 16F87XA — 1.6 4 mA XT, RC osc configurations,
D010A 16LF87XA — 20 35 μA LP osc configuration,
FOSC = 32 kHz, VDD = 3.0V,
WDT disabled
D013 16F87XA — 7 15 mA HS osc configuration,
D015 ΔIBOR Brown-out
Reset Current(6)
— 85 200 μA BOR enabled, VDD = 5.0V

PIC16F87XA
PIC16LF873A/874A/876A/877A
(Industrial)
PIC16F873A/874A/876A/877A
Symbol
Characteristic/
Device
IPD Power-down Current(3,5)
Param
No.
D020 16LF87XA — 7.5 30 μA VDD = 3.0V, WDT enabled,
-40°C to +85°C
D020 16F87XA — 10.5 42
60
μA
μA
VDD = 4.0V, WDT enabled,
-40°C to +85°C
VDD = 4.0V, WDT enabled,
-40°C to +125°C (extended)
D021 16LF87XA — 0.9 5 μA VDD = 3.0V, WDT disabled,
0°C to +70°C
D021 16F87XA — 1.5 16
20
μA
μA
VDD = 4.0V, WDT disabled,
-40°C to +85°C
VDD = 4.0V, WDT disabled,
-40°C to +125°C (extended)
D021A 16LF87XA 0.9 5 μA VDD = 3.0V, WDT disabled,
-40°C to +85°C
D021A 16F87XA 1.5 19 μA VDD = 4.0V, WDT disabled,
-40°C to +85°C
D023 ΔIBOR Brown-out
Reset Current(6)
— 85 200 μA BOR enabled, VDD = 5.0V

PIC16F87XA
PIC16LF873A/874A/876A/877A (Industrial)
DC CHARACTERISTICS
Operating voltage VDD range as described in DC specification
(Section 17.1)
Param
No.
Sym Characteristic Min Typ† Max Units Conditions
VIL Input Low Voltage
I/O ports:
D030 with TTL buffer VSS — 0.15 VDD V For entire VDD range
D030A VSS — 0.8V V 4.5V ≤ VDD ≤ 5.5V
D031 with Schmitt Trigger buffer VSS — 0.2 VDD V
D032 MCLR, OSC1 (in RC mode) VSS — 0.2 VDD V
D033 OSC1 (in XT and LP modes) VSS — 0.3V V (Note 1)
OSC1 (in HS mode) VSS — 0.3 VDD V
Ports RC3 and RC4: —
D034 with Schmitt Trigger buffer VSS — 0.3 VDD V For entire VDD range
D034A with SMBus -0.5 — 0.6 V For VDD = 4.5 to 5.5V
VIH Input High Voltage
I/O ports: —
D040 with TTL buffer 2.0 — VDD V 4.5V ≤ VDD ≤ 5.5V
D040A 0.25 VDD
+ 0.8V
— VDD V For entire VDD range
D041 with Schmitt Trigger buffer 0.8 VDD — VDD V For entire VDD range
D042 MCLR 0.8 VDD — VDD V
D042A OSC1 (in XT and LP modes) 1.6V — VDD V (Note 1)
OSC1 (in HS mode) 0.7 VDD — VDD V
D043 OSC1 (in RC mode) 0.9 VDD — VDD V
Ports RC3 and RC4:
D044 with Schmitt Trigger buffer 0.7 VDD — VDD V For entire VDD range
D044A with SMBus 1.4 — 5.5 V For VDD = 4.5 to 5.5V
D070 IPURB PORTB Weak Pull-up Current 50 250 400 μA VDD = 5V, VPIN = VSS,
-40°C TO +85°C
IIL Input Leakage Current(2, 3)
D060 I/O ports — — ±1 μA VSS ≤ VPIN ≤ VDD,
pin at high-impedance
D061 MCLR, RA4/T0CKI — — ±5 μA VSS ≤ VPIN ≤ VDD
D063 OSC1 — — ±5 μA VSS ≤ VPIN ≤ VDD, XT, HS
and LP osc configuration
* These parameters are characterized but not tested.
† Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance
Note 1: In RC oscillator configuration, the OSC1/CLKI pin is a Schmitt Trigger input. It is not recommended that the
PIC16F87XA be driven with external clock in RC mode.
2: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified levels
represent normal operating conditions. Higher leakage current may be measured at different input voltages.
3: Negative current is defined as current sourced by the pin.

PIC16F87XA
DC CHARACTERISTICS
VOL Output Low Voltage
Operating voltage VDD range as described in DC specification
(Section 17.1)
Param
No.
D080 I/O ports — — 0.6 V IOL = 8.5 mA, VDD = 4.5V,
-40°C to +85°C
D083 OSC2/CLKO (RC osc config) — — 0.6 V IOL = 1.6 mA, VDD = 4.5V,
-40°C to +85°C
VOH Output High Voltage
D090 I/O ports(3) VDD – 0.7 — — V IOH = -3.0 mA, VDD = 4.5V,
-40°C to +85°C
D092 OSC2/CLKO (RC osc config) VDD – 0.7 — — V IOH = -1.3 mA, VDD = 4.5V,
-40°C to +85°C
D150* VOD Open-Drain High Voltage — — 8.5 V RA4 pin
Capacitive Loading Specs on
Output Pins
D100 COSC2 OSC2 pin — — 15 pF In XT, HS and LP modes when
external clock is used to drive
OSC1
D101
D102
CIO
CB
All I/O pins and OSC2 (RC mode)
SCL, SDA (I2C mode)
—
—
—
—
50
400
pF
pF
Data EEPROM Memory
D120 ED Endurance 100K 1M — E/W -40°C to +85°C
D121 VDRW VDD for read/write VMIN — 5.5 V Using EECON to read/write,
VMIN = min. operating voltage
D122 TDEW Erase/write cycle time — 4 8 ms
Program Flash Memory
D130 EP Endurance 10K 100K — E/W -40°C to +85°C
D131 VPR VDD for read VMIN — 5.5 V VMIN = min. operating voltage
D132A VDD for erase/write VMIN — 5.5 V Using EECON to read/write,
VMIN = min. operating voltage
D133 TPEW Erase/Write cycle time — 4 8 ms
Note 1: In RC oscillator configuration, the OSC1/CLKI pin is a Schmitt Trigger input. It is not recommended that the
PIC16F87XA be driven with external clock in RC mode.
2: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified levels
represent normal operating conditions. Higher leakage current may be measured at different input voltages.
3: Negative current is defined as current sourced by the pin.

PIC16F87XA
TABLE 17-1: COMPARATOR SPECIFICATIONS
Operating Conditions: 3.0V < VDD < 5.5V, -40°C < TA < +85°C (unless otherwise stated)
4.0V < VDD < 5.5V, -40°C < TA < +125°C (unless otherwise stated)
Param
No.
Sym Characteristics Min Typ Max Units Comments
D300 VIOFF Input Offset Voltage — ± 5.0 ± 10 mV
D301 VICM Input Common Mode Voltage* 0 - VDD – 1.5 V
D302 CMRR Common Mode Rejection Ratio* 55 - — dB
300
TRESP Response Time*(1) — 150 400
300A
301 TMC2OV Comparator Mode Change to
Output Valid*
— — 10 μs
Note 1: Response time measured with one comparator input at (VDD – 1.5)/2 while the other input transitions from
VSS to VDD.
TABLE 17-2: VOLTAGE REFERENCE SPECIFICATIONS
600
ns
ns
PIC16F87XA
PIC16LF87XA
Operating Conditions: 3.0V < VDD < 5.5V, -40°C < TA < +85°C (unless otherwise stated)
4.0V < VDD < 5.5V, -40°C < TA < +125°C (unless otherwise stated)
Spec
No.
Sym Characteristics Min Typ Max Units Comments
D310 VRES Resolution VDD/24 — VDD/32 LSb
D311 VRAA Absolute Accuracy —
—
—
—
1/2
1/2
LSb
LSb
Low Range (VRR = 1)
High Range (VRR = 0)
D312 VRUR Unit Resistor Value (R)* — 2k — Ω
310 TSET Settling Time*(1) — — 10 μs
Note 1: Settling time measured while VRR = 1 and VR<3:0> transitions from ‘0000’ to ‘1111’.

PIC16F87XA
17.3 Timing Parameter Symbology
The timing parameter symbols have been created
following one of the following formats:
1. TppS2ppS 3. TCC:ST (I2C specifications only)
2. TppS 4. Ts (I2C specifications only)
T
F Frequency T Time
Lowercase letters (pp) and their meanings:
pp
cc CCP1 osc OSC1
ck CLKO rd RD
cs CS rw RD or WR
di SDI sc SCK
do SDO ss SS
dt Data in t0 T0CKI
io I/O port t1 T1CKI
mc MCLR wr WR
Uppercase letters and their meanings:
S
F Fall P Period
H High R Rise
I Invalid (High-impedance) V Valid
L Low Z High-impedance
I2C only
AA output access High High
BUF Bus free Low Low
TCC:ST (I2C specifications only)
CC
HD Hold SU Setup
ST
DAT Data input hold STO Stop condition
STA Start condition
FIGURE 17-3: LOAD CONDITIONS
Load Condition 1 Load Condition 2
VDD/2
RL
CL
Pin Pin
VSS VSS
CL
RL = 464Ω
CL = 50 pF for all pins except OSC2, but including PORTD and PORTE outputs as ports,
15 pF for OSC2 output
Note: PORTD and PORTE are not implemented on PIC16F873A/876A devices.

PIC16F87XA
FIGURE 17-4: EXTERNAL CLOCK TIMING
OSC1
CLKO
Q4 Q1 Q2 Q3 Q4 Q1
1
2
3 3 4 4
TABLE 17-3: EXTERNAL CLOCK TIMING REQUIREMENTS
Param
No.
Symbol Characteristic Min Typ† Max Units Conditions
FOSC External CLKI Frequency
(Note 1)
DC — 1 MHz XT and RC Osc mode
DC — 20 MHz HS Osc mode
DC — 32 kHz LP Osc mode
Oscillator Frequency
(Note 1)
DC — 4 MHz RC Osc mode
0.1 — 4 MHz XT Osc mode
4
—
20
MHz
HS Osc mode
5
—
200
kHz
LP Osc mode
1 TOSC External CLKI Period
(Note 1)
1000 — — ns XT and RC Osc mode
50 — — ns HS Osc mode
5 — — μs LP Osc mode
Oscillator Period
(Note 1)
250 — — ns RC Osc mode
250 — 1 μs XT Osc mode
100 — 250 ns HS Osc mode
50 — 250 ns HS Osc mode
31.25 — — μs LP Osc mode
2 TCY Instruction Cycle Time
(Note 1)
200 TCY DC ns TCY = 4/FOSC
3 TOSL,
TOSH
External Clock in (OSC1) High or
Low Time
100 — — ns XT oscillator
2.5 — — μs LP oscillator
15 — — ns HS oscillator
4 TOSR,
TOSF
External Clock in (OSC1) Rise or
Fall Time
— — 25 ns XT oscillator
— — 50 ns LP oscillator
— — 15 ns HS oscillator
Note 1: Instruction cycle period (TCY) equals four times the input oscillator time base period. All specified values are
based on characterization data for that particular oscillator type, under standard operating conditions, with
the device executing code. Exceeding these specified limits may result in an unstable oscillator operation
and/or higher than expected current consumption. All devices are tested to operate at “min.” values with an
external clock applied to the OSC1/CLKI pin. When an external clock input is used, the “max.” cycle time
limit is “DC” (no clock) for all devices.

PIC16F87XA
FIGURE 17-5: CLKO AND I/O TIMING
OSC1
CLKO
I/O pin
(Input)
I/O pin
(Output)
Q4 Q1 Q2 Q3
10
13
17
Old Value New Value
Note: Refer to Figure 17-3 for load conditions.
14
20, 21
19 18
TABLE 17-4: CLKO AND I/O TIMING REQUIREMENTS
15
11
12
16
Param
No.
10* TOSH2CKL OSC1 ↑ to CLKO ↓ — 75 200 ns (Note 1)
11* TOSH2CKH OSC1 ↑ to CLKO ↑ — 75 200 ns (Note 1)
12* TCKR CLKO Rise Time — 35 100 ns (Note 1)
13* TCKF CLKO Fall Time — 35 100 ns (Note 1)
14* TCKL2IOV CLKO ↓ to Port Out Valid — — 0.5 TCY + 20 ns (Note 1)
15* TIOV2CKH Port In Valid before CLKO ↑ TOSC + 200 — — ns (Note 1)
16* TCKH2IOI Port In Hold after CLKO ↑ 0 — — ns (Note 1)
17* TOSH2IOV OSC1 ↑ (Q1 cycle) to Port Out Valid — 100 255 ns
18* TOSH2IOI OSC1 ↑ (Q2 cycle) to Port Input
Invalid (I/O in hold time)
Standard (F) 100 — — ns
Extended (LF) 200 — — ns
19* TIOV2OSH Port Input Valid to OSC1 ↑ (I/O in setup time) 0 — — ns
20* TIOR Port Output Rise Time Standard (F) — 10 40 ns
Extended (LF) — — 145 ns
21* TIOF Port Output Fall Time Standard (F) — 10 40 ns
Extended (LF) — — 145 ns
22††* TINP INT pin High or Low Time TCY — — ns
23††* TRBP RB7:RB4 Change INT High or Low Time TCY — — ns
† Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only and are
not tested.
†† These parameters are asynchronous events not related to any internal clock edges.
Note 1: Measurements are taken in RC mode where CLKO output is 4 x TOSC.

PIC16F87XA
FIGURE 17-6: RESET, WATCHDOG TIMER, OSCILLATOR START-UP TIMER AND POWER-UP
TIMER TIMING
VDD
MCLR
Internal
POR
PWRT
Time-out
OSC
Time-out
Internal
Reset
Watchdog
Timer
Reset
33
32
I/O pins
FIGURE 17-7: BROWN-OUT RESET TIMING
30
31
34
34
VDD VBOR
35
TABLE 17-5: RESET, WATCHDOG TIMER, OSCILLATOR START-UP TIMER, POWER-UP TIMER
AND BROWN-OUT RESET REQUIREMENTS
Param
No.
30 TMCL MCLR Pulse Width (low) 2 — — μs VDD = 5V, -40°C to +85°C
31* TWDT Watchdog Timer Time-out Period
(no prescaler)
7 18 33 ms VDD = 5V, -40°C to +85°C
32 TOST Oscillation Start-up Timer Period — 1024 TOSC — — TOSC = OSC1 period
33* TPWRT Power-up Timer Period 28 72 132 ms VDD = 5V, -40°C to +85°C
34 TIOZ I/O High-Impedance from MCLR Low
or Watchdog Timer Reset
— — 2.1 μs
35 TBOR Brown-out Reset Pulse Width 100 — — μs VDD ≤ VBOR (D005)
not tested.

PIC16F87XA
FIGURE 17-8: TIMER0 AND TIMER1 EXTERNAL CLOCK TIMINGS
RA4/T0CKI
RC0/T1OSO/T1CKI
TMR0 or TMR1
41
46
42
47
40
45
TABLE 17-6: TIMER0 AND TIMER1 EXTERNAL CLOCK REQUIREMENTS
Param
No.
48
40* TT0H T0CKI High Pulse Width No Prescaler 0.5 TCY + 20 — — ns Must also meet
With Prescaler 10 — — ns parameter 42
41* TT0L T0CKI Low Pulse Width No Prescaler 0.5 TCY + 20 — — ns Must also meet
With Prescaler 10 — — ns parameter 42
42* TT0P T0CKI Period No Prescaler TCY + 40 — — ns
With Prescaler Greater of:
20 or TCY + 40
N
— — ns N = prescale value
(2, 4,..., 256)
45* TT1H T1CKI High
Time
Synchronous, Prescaler = 1 0.5 TCY + 20 — — ns Must also meet
Synchronous, parameter 47
Prescaler = 2, 4, 8
Standard(F) 15 — — ns
Extended(LF) 25 — — ns
Asynchronous Standard(F) 30 — — ns
46* TT1L T1CKI Low Time Synchronous, Prescaler = 1 0.5 TCY + 20 — — ns Must also meet
Synchronous, parameter 47
Prescaler = 2, 4, 8
47* TT1P T1CKI Input
Period
Synchronous Standard(F) Greater of:
30 or TCY + 40
N
(1, 2, 4, 8)
Extended(LF) Greater of:
50 or TCY + 40
N
N = prescale value
(1, 2, 4, 8)
FT1 Timer1 Oscillator Input Frequency Range
(oscillator enabled by setting bit T1OSCEN)
DC — 200 kHz
48 TCKEZTMR1 Delay from External Clock Edge to Timer Increment 2 TOSC — 7 TOSC —
not tested.

PIC16F87XA
FIGURE 17-9: CAPTURE/COMPARE/PWM TIMINGS (CCP1 AND CCP2)
RC1/T1OSI/CCP2
and RC2/CCP1
(Capture Mode)
53 54
RC1/T1OSI/CCP2
and RC2/CCP1
(Compare or PWM Mode)
50 51
52
TABLE 17-7: CAPTURE/COMPARE/PWM REQUIREMENTS (CCP1 AND CCP2)
Param
No.
50* TCCL CCP1 and CCP2
Input Low Time
No Prescaler 0.5 TCY + 20 — — ns
With Prescaler
51* TCCH CCP1 and CCP2
Input High Time
No Prescaler 0.5 TCY + 20 — — ns
With Prescaler
52* TCCP CCP1 and CCP2 Input Period 3 TCY + 40
N
(1, 4 or 16)
53* TCCR CCP1 and CCP2 Output Rise Time Standard(F) — 10 25 ns
Extended(LF) — 25 50 ns
54* TCCF CCP1 and CCP2 Output Fall Time Standard(F) — 10 25 ns
Extended(LF) — 25 45 ns
not tested.

PIC16F87XA
FIGURE 17-10: PARALLEL SLAVE PORT TIMING (PIC16F874A/877A ONLY)
RE2/CS
RE0/RD
RE1/WR
RD7:RD0
64
62
63
65
TABLE 17-8: PARALLEL SLAVE PORT REQUIREMENTS (PIC16F874A/877A ONLY)
Param
No.
62 TDTV2WRH Data In Valid before WR ↑ or CS ↑ (setup time) 20 — — ns
63* TWRH2DTI WR↑ or CS ↑ to Data–in Invalid
(hold time)
64 TRDL2DTV RD↓ and CS ↓ to Data–out Valid — — 80 ns
65 TRDH2DTI RD↑ or CS ↓ to Data–out Invalid 10 — 30 ns
not tested.

PIC16F87XA
FIGURE 17-11: SPI MASTER MODE TIMING (CKE = 0, SMP = 0)
SS
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
SDI
70
71 72
78 79
79 78 80
MSb In Bit 6 - - - -1 LSb In
73
MSb Bit 6 - - - - - -1 LSb
74
75, 76
FIGURE 17-12: SPI MASTER MODE TIMING (CKE = 1, SMP = 1)
SS
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
SDI
81
71 72
MSb
MSb In
74
80
75, 76
79
78
73
Bit 6 - - - - - -1
LSb
Bit 6 - - - -1 LSb In

PIC16F87XA
FIGURE 17-13: SPI SLAVE MODE TIMING (CKE = 0)
SS
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
70
71 72
78 79
79 78 80
83
73
MSb Bit 6 - - - - - -1 LSb
74
75, 76 77
SDI
FIGURE 17-14: SPI SLAVE MODE TIMING (CKE = 1)
SS
SCK
(CKP = 0)
SCK
(CKP = 1)
SDO
82
70
71 72
SDI
80
MSb Bit 6 - - - - - -1 LSb
74
75, 76
77
83

PIC16F87XA
TABLE 17-9: SPI MODE REQUIREMENTS
Param
No.
70* TSSL2SCH,
TSSL2SCL
SS ↓ to SCK ↓ or SCK ↑ Input TCY — — ns
71* TSCH SCK Input High Time (Slave mode) TCY + 20 — — ns
72* TSCL SCK Input Low Time (Slave mode) TCY + 20 — — ns
73* TDIV2SCH,
TDIV2SCL
Setup Time of SDI Data Input to SCK Edge 100 — — ns
74* TSCH2DIL,
TSCL2DIL
Hold Time of SDI Data Input to SCK Edge 100 — — ns
75* TDOR SDO Data Output Rise Time Standard(F)
Extended(LF)
76* TDOF SDO Data Output Fall Time — 10 25 ns
77* TSSH2DOZ SS↑ to SDO Output High-Impedance 10 — 50 ns
78* TSCR SCK Output Rise Time
(Master mode)
Standard(F)
Extended(LF)
79* TSCF SCK Output Fall Time (Master mode) — 10 25 ns
80* TSCH2DOV,
TSCL2DOV
SDO Data Output Valid after
SCK Edge
Standard(F)
Extended(LF)
81* TDOV2SCH,
TDOV2SCL
SDO Data Output Setup to SCK Edge TCY — — ns
82* TSSL2DOV SDO Data Output Valid after SS ↓ Edge — — 50 ns
83* TSCH2SSH,
TSCL2SSH
SS ↑ after SCK Edge 1.5 TCY + 40 — — ns
not tested.
FIGURE 17-15: I2C BUS START/STOP BITS TIMING
—
—
10
25
25
50
ns
ns
—
—
10
25
25
50
ns
ns
—
—
—
—
50
145
ns
91 93
SCL
SDA
90 92
Start
Condition
Stop
Condition

PIC16F87XA
TABLE 17-10: I2C BUS START/STOP BITS REQUIREMENTS
Param
No.
Symbol Characteristic Min Typ Max Units Conditions
90 TSU:STA Start condition 100 kHz mode 4700 — — ns Only relevant for Repeated Start
Setup time 400 kHz mode 600 — — condition
91 THD:STA Start condition 100 kHz mode 4000 — — ns After this period, the first clock pulse
Hold time 400 kHz mode 600 — — is generated
92 TSU:STO Stop condition 100 kHz mode 4700 — — ns
Setup time 400 kHz mode 600 — —
93 THD:STO Stop condition 100 kHz mode 4000 — — ns
Hold time 400 kHz mode 600 — —
FIGURE 17-16: I2C BUS DATA TIMING
90
100
101
103
106
107
91 92
109 109
SCL
SDA
In
SDA
Out
110
102

PIC16F87XA
TABLE 17-11: I2C BUS DATA REQUIREMENTS
Param
No.
Sym Characteristic Min Max Units Conditions
100 THIGH Clock High Time 100 kHz mode 4.0 — μs
400 kHz mode 0.6 — μs
SSP Module 0.5 TCY —
101 TLOW Clock Low Time 100 kHz mode 4.7 — μs
SSP Module 0.5 TCY —
102 TR SDA and SCL Rise
Time
100 kHz mode — 1000 ns
400 kHz mode 20 + 0.1 CB 300 ns Cb is specified to be from 10 to
400 pF
103 TF SDA and SCL Fall
Time
100 kHz mode — 300 ns
400 kHz mode 20 + 0.1 CB 300 ns CB is specified to be from 10 to
400 pF
90 TSU:STA Start Condition Setup
Time
100 kHz mode 4.7 — μs Only relevant for Repeated Start
400 kHz mode 0.6 — μs condition
91 THD:STA Start Condition Hold
Time
100 kHz mode 4.0 — μs After this period, the first clock
400 kHz mode 0.6 — μs pulse is generated
106 THD:DAT Data Input Hold Time 100 kHz mode 0 — ns
400 kHz mode 0 0.9 μs
107 TSU:DAT Data Input Setup Time 100 kHz mode 250 — ns (Note 2)
400 kHz mode 100 — ns
92 TSU:STO Stop Condition Setup
Time
109 TAA Output Valid from
Clock
100 kHz mode — 3500 ns (Note 1)
400 kHz mode — — ns
110 TBUF Bus Free Time 100 kHz mode 4.7 — μs Time the bus must be free before
400 kHz mode 1.3 — μs a new transmission can start
CB Bus Capacitive Loading — 400 pF
Note 1: As a transmitter, the device must provide this internal minimum delay time to bridge the undefined region (min. 300 ns)
of the falling edge of SCL to avoid unintended generation of Start or Stop conditions.
2: A fast mode (400 kHz) I2C bus device can be used in a standard mode (100 kHz) I2C bus system, but the requirement
that, TSU:DAT ≥ 250 ns, must then be met. This will automatically be the case if the device does not stretch the LOW
period of the SCL signal. If such a device does stretch the LOW period of the SCL signal, it must output the next data bit
to the SDA line, TR MAX. + TSU:DAT = 1000 + 250 = 1250 ns (according to the standard mode I2C bus specification),
before the SCL line is released.

PIC16F87XA
FIGURE 17-17: USART SYNCHRONOUS TRANSMISSION (MASTER/SLAVE) TIMING
121
RC6/TX/CK
pin
RC7/RX/DT
pin
120
121
122
TABLE 17-12: USART SYNCHRONOUS TRANSMISSION REQUIREMENTS
Param
No.
120 TCKH2DTV SYNC XMIT (MASTER & SLAVE)
Clock High to Data Out Valid Standard(F) — — 80 ns
Extended(LF) — — 100 ns
121 TCKRF Clock Out Rise Time and Fall Time
(Master mode)
Standard(F) — — 45 ns
122 TDTRF Data Out Rise Time and Fall Time Standard(F) — — 45 ns
FIGURE 17-18: USART SYNCHRONOUS RECEIVE (MASTER/SLAVE) TIMING
125
RC6/TX/CK
pin
RC7/RX/DT
pin
126
TABLE 17-13: USART SYNCHRONOUS RECEIVE REQUIREMENTS
Param
No.
125 TDTV2CKL SYNC RCV (MASTER & SLAVE)
Data Setup before CK ↓ (DT setup time) 15 — — ns
126 TCKL2DTL Data Hold after CK ↓ (DT hold time) 15 — — ns

PIC16F87XA
TABLE 17-14: A/D CONVERTER CHARACTERISTICS:PIC16F873A/874A/876A/877A (INDUSTRIAL)
PIC16LF873A/874A/876A/877A (INDUSTRIAL)
Param
No.
A01 NR Resolution — — 10-bits bit VREF = VDD = 5.12V,
VSS ≤ VAIN ≤ VREF
A03 EIL Integral Linearity Error — — < ± 1 LSb VREF = VDD = 5.12V,
A04 EDL Differential Linearity Error — — < ± 1 LSb VREF = VDD = 5.12V,
A06 EOFF Offset Error — — < ± 2 LSb VREF = VDD = 5.12V,
A07 EGN Gain Error — — < ± 1 LSb VREF = VDD = 5.12V,
A10 — Monotonicity — guaranteed(3) — — VSS ≤ VAIN ≤ VREF
A20 VREF Reference Voltage (VREF+ – VREF-) 2.0 — VDD + 0.3 V
A21 VREF+ Reference Voltage High AVDD – 2.5V AVDD + 0.3V V
A22 VREF- Reference Voltage Low AVSS – 0.3V VREF+ – 2.0V V
A25 VAIN Analog Input Voltage VSS – 0.3V — VREF + 0.3V V
A30 ZAIN Recommended Impedance of
Analog Voltage Source
— — 2.5 kΩ (Note 4)
A40 IAD A/D Conversion
Current (VDD)
PIC16F87XA — 220 — μA Average current
consumption when A/D is
on (Note 1)
PIC16LF87XA — 90 — μA
A50 IREF VREF Input Current (Note 2) —
—
—
—
5
150
μA
μA
During VAIN acquisition.
Based on differential of
VHOLD to VAIN to charge
CHOLD, see Section 11.1
“A/D Acquisition
Requirements”.
During A/D conversion
cycle
not tested.
Note 1: When A/D is off, it will not consume any current other than minor leakage current. The power-down current spec
includes any such leakage from the A/D module.
2: VREF current is from RA3 pin or VDD pin, whichever is selected as reference input.
3: The A/D conversion result never decreases with an increase in the input voltage and has no missing codes.
4: Maximum allowed impedance for analog voltage source is 10 kΩ. This requires higher acquisition time.

PIC16F87XA
FIGURE 17-19: A/D CONVERSION TIMING
BSF ADCON0, GO
132
Q4
A/D CLK
A/D DATA
ADRES
ADIF
GO
SAMPLE
1 TCY
. . . . . .
9 8 7 2 1 0
OLD_DATA
Sampling Stopped
(TOSC/2)(1)
Note: If the A/D clock source is selected as RC, a time of TCY is added before the A/D clock starts. This allows the SLEEP
instruction to be executed.
TABLE 17-15: A/D CONVERSION REQUIREMENTS
131
130
NEW_DATA
DONE
Param
No.
130 TAD A/D Clock Period PIC16F87XA 1.6 — — μs TOSC based, VREF ≥ 3.0V
PIC16LF87XA 3.0 — — μs TOSC based, VREF ≥ 2.0V
PIC16F87XA 2.0 4.0 6.0 μs A/D RC mode
PIC16LF87XA 3.0 6.0 9.0 μs A/D RC mode
131 TCNV Conversion Time (not including S/H time)
(Note 1)
— 12 TAD
132 TACQ Acquisition Time (Note 2)
10*
40
—
—
—
μs
μs The minimum time is the
amplifier settling time. This may
be used if the “new” input volt-age
has not changed by more
than 1 LSb (i.e., 20.0 mV @
5.12V) from the last sampled
voltage (as stated on CHOLD).
134 TGO Q4 to A/D Clock Start — TOSC/2 § — — If the A/D clock source is
selected as RC, a time of TCY is
added before the A/D clock
starts. This allows the SLEEP
instruction to be executed.
not tested.
§ This specification ensured by design.
Note 1: ADRES register may be read on the following TCY cycle.
2: See Section 11.1 “A/D Acquisition Requirements” for minimum conditions.

PIC16F87XA
NOTES:

PIC16F87XA
18.0 DC AND AC CHARACTERISTICS GRAPHS AND TABLES
Note: The graphs and tables provided following this note are a statistical summary based on a limited number of
samples and are provided for informational purposes only. The performance characteristics listed herein
are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified
operating range (e.g., outside specified power supply range) and therefore, outside the warranted range.
“Typical” represents the mean of the distribution at 25°C. “Maximum” or “minimum” represents (mean + 3σ) or (mean – 3σ)
respectively, where σ is a standard deviation, over the whole temperature range.
FIGURE 18-1: TYPICAL IDD vs. FOSC OVER VDD (HS MODE)
7
6
5
4
3
2
1
0
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
2.0V
Typical: statistical mean @ 25°C
Maximum: mean + 3σ (-40°C to +125°C)
Minimum: mean – 3σ (-40°C to +125°C)
4 6 8 10 12 14 16 18 20
FOSC (MHz)
IDD (mA)
FIGURE 18-2: MAXIMUM IDD vs. FOSC OVER VDD (HS MODE)
8
7
6
5
4
3
2
1
0
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
2.0V
4 6 8 10 12 14 16 18 20
FOSC (MHz)
IDD (mA)

PIC16F87XA
FIGURE 18-3: TYPICAL IDD vs. FOSC OVER VDD (XT MODE)
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
2.0V
0 500 1000 1500 2000 2500 3000 3500 4000
FOSC (MHz)
IDD (mA)
FIGURE 18-4: MAXIMUM IDD vs. FOSC OVER VDD (XT MODE)
2.5
2.0
1.5
1.0
0.5
0.0
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
2.0V
0 500 1000 1500 2000 2500 3000 3500 4000
FOSC (MHz)
IDD (mA)

PIC16F87XA
FIGURE 18-5: TYPICAL IDD vs. FOSC OVER VDD (LP MODE)
70
60
50
40
30
20
10
0
5.5V
5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
2.0V
20 30 40 50 60 70 80 90 100
FOSC (kHz)
IDD (uA)
FIGURE 18-6: MAXIMUM IDD vs. FOSC OVER VDD (LP MODE)
120
100
80
Typical: statistical mean @ 25°C 5.5V
uA)
(60
IDD 40
20
0
FOSC (kHz) 5.0V
4.5V
4.0V
3.5V
3.0V
2.5V
2.0V
20 30 40 50 60 70 80 90 100

PIC16F87XA
FIGURE 18-7: AVERAGE FOSC vs. VDD FOR VARIOUS VALUES OF R (RC MODE, C = 20 pF, +25°C)
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
5.1 kOhm
10 kOhm
100 kOhm
Operation above 4 MHz is not recommended
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VDD (V)
Freq (MHz)
FIGURE 18-8: AVERAGE FOSC vs. VDD FOR VARIOUS VALUES OF R
(RC MODE, C = 100 pF, +25°C)
2.5
2.0
1.5
1.0
0.5
0.0
3.3 kOhm
5.1 kOhm
10 kOhm
100 kOhm
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VDD (V)
Freq (MHz)

PIC16F87XA
FIGURE 18-9: AVERAGE FOSC vs. VDD FOR VARIOUS VALUES OF R
(RC MODE, C = 300 pF, +25°C)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
3.3 kOhm
5.1 kOhm
10 kOhm
100 kOhm
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VDD (V)
Freq (MHz)
FIGURE 18-10: IPD vs. VDD, -40°C TO +125°C (SLEEP MODE, ALL PERIPHERALS DISABLED)
100
10
1
Max (125°C)
Max (85°C)
uA)
(IPD 0.1
0.01
0.001
VDD (V) Typ (25°C)
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

PIC16F87XA
FIGURE 18-11: TYPICAL AND MAXIMUM ΔITMR1 vs. VDD OVER TEMPERATURE (-10°C TO +70°C,
TIMER1 WITH OSCILLATOR, XTAL = 32 kHz, C1 AND C2 = 47 pF)
14
12
10
8
6
4
2
0
Max (+70°C)
Max (70C)
Typ (+25°C)
Typ (25C)
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VDD (V)
(μA)
IPD uA)
FIGURE 18-12: TYPICAL AND MAXIMUM ΔIWDT vs. VDD OVER TEMPERATURE (WDT ENABLED)
100
10
1
0.1
Max (+125°C)
Max (+85°C)
Typ (+25°C)
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VDD (V)
IPD (uA)

PIC16F87XA
FIGURE 18-13: ΔIBOR vs. VDD OVER TEMPERATURE
1,000
100
10
Max (125°C)
Typ (25°C)
Device in
Reset
Device in
Indeterminant Sleep
State
Max (125°C)
Note: Device current in Reset
depends on oscillator mode,
frequency and circuit.
Typical: statistical mean @ 25°C Typ (25°C)
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VDD (V)
IDD (μA)
FIGURE 18-14: TYPICAL, MINIMUM AND MAXIMUM WDT PERIOD vs. VDD (-40°C TO +125°C)
50
45
40
35
30
ms)
(Period 25
WDT 20
15
10
5
0
VDD (V) Typical: statistical mean @ 25°C
Max
(125°C)
Typ
(25°C)
Min
(-40°C)
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

PIC16F87XA
FIGURE 18-15: AVERAGE WDT PERIOD vs. VDD OVER TEMPERATURE (-40°C TO +125°C)
50
45
40
35
30
25
20
15
10
5
0
125°C
85°C
25°C
-40°C
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VDD (V)
WDT Period (ms)
FIGURE 18-16: TYPICAL, MINIMUM AND MAXIMUM VOH vs. IOH (VDD = 5V, -40°C TO +125°C)
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Max
Typ (25°C)
Min
0 5 10 15 20 25
IOH (-mA)
VOH (V)

PIC16F87XA
FIGURE 18-17: TYPICAL, MINIMUM AND MAXIMUM VOH vs. IOH (VDD = 3V, -40°C TO +125°C)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Max
Typ (25°C)
Min
0 5 10 15 20 25
IOH (-mA)
VOH (V)
FIGURE 18-18: TYPICAL, MINIMUM AND MAXIMUM VOL vs. IOL (VDD = 5V, -40°C TO +125°C)
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Max (125°C)
Max (85°C)
Typ (25°C)
Min (-40°C)
0 5 10 15 20 25
IOL (-mA)
VOL (V)

PIC16F87XA
FIGURE 18-19: TYPICAL, MINIMUM AND MAXIMUM VOL vs. IOL (VDD = 3V, -40°C TO +125°C)
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Max (125°C)
Max (85°C)
Typ (25°C)
Min (-40°C)
0 5 10 15 20 25
IOL (-mA)
VOL (V)
FIGURE 18-20: MINIMUM AND MAXIMUM VIN vs. VDD (TTL INPUT, -40°C TO +125°C)
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
VTH Max (-40°C)
VTH Typ (25°C)
VTH Min (125°C)
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VDD (V)
VIN (V)

PIC16F87XA
FIGURE 18-21: MINIMUM AND MAXIMUM VIN vs. VDD (ST INPUT, -40°C TO +125°C)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
VIH Max (125°C)
VIH Min (-40°C)
VIL Max (-40°C)
VIL Min (125°C)
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VDD (V)
VIN (V)
FIGURE 18-22: MINIMUM AND MAXIMUM VIN vs. VDD (I2C INPUT, -40°C TO +125°C)
3.5
3.0
2.5
2.0
VIL Max
VILMax
V)
(VIN 1.5
1.0
0.5
0.0
VDD (V) VIH Max
VIH Min
VIL Min
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

PIC16F87XA
FIGURE 18-23: A/D NONLINEARITY vs. VREFH (VDD = VREFH, -40°C TO +125°C)
4
3.5
3
2.5
2
1.5
1
0.5
0
-40°C
-40C
+25°C
25C
+85°C
85C
+125°C
125C
2 2.5 3 3.5 4 4.5 5 5.5
VDD and VREFH (V)
Differential or Integral Nonlinearity (LSB)
FIGURE 18-24: A/D NONLINEARITY vs. VREFH (VDD = 5V, -40°C TO +125°C)
3
2.5
2
1.5
1
0.5
0
Max (-40°C to +125°C)
Max (-40C to 125C)
TTyypp ((+2255C°)C)
2 2.5 3 3.5 4 4.5 5 5.5
VREFH (V)
Differential or Integral Nonlinearilty (LSB)

PIC16F87XA
19.0 PACKAGING INFORMATION
19.1 Package Marking Information
40-Lead PDIP
XXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXX
YYWWNNN
Example
PIC16F877A/P
0310017
44-Lead TQFP
XXXXXXXXXX
XXXXXXXXXX
XXXXXXXXXX
YYWWNNN
Example
PIC16F877A
/PT
0310017
44-Lead PLCC
XXXXXXXXXX
XXXXXXXXXX
XXXXXXXXXX
YYWWNNN
Example
PIC16F877A
-20/L
0310017
Legend: XX...X Customer specific information*
Y Year code (last digit of calendar year)
YY Year code (last 2 digits of calendar year)
WW Week code (week of January 1 is week ‘01’)
NNN Alphanumeric traceability code
Note: In the event the full Microchip part number cannot be marked on one line, it will
be carried over to the next line thus limiting the number of available characters
for customer specific information.
* Standard PICmicro device marking consists of Microchip part number, year code, week code, and
traceability code. For PICmicro device marking beyond this, certain price adders apply. Please check
with your Microchip Sales Office. For QTP devices, any special marking adders are included in QTP
price.

PIC16F87XA
Package Marking Information (Cont’d)
44-Lead QFN
XXXXXXXXXX
XXXXXXXXXX
XXXXXXXXXX
YYWWNNN
Example
28-Lead PDIP (Skinny DIP)
XXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXX
YYWWNNN
PIC16F877A
-I/ML
0310017
Example
PIC16F876A/SP
0310017
28-Lead SOIC
XXXXXXXXXXXXXXXXXXXX
YYWWNNN
Example
PIC16F876A/SO
0310017
28-Lead SSOP
XXXXXXXXXXXX
XXXXXXXXXXXX
YYWWNNN
Example
PIC16F876A/
SS
0310017
28-Lead QFN Example
XXXXXXXX
XXXXXXXX
YYWWNNN
16F873A
-I/ML
0310017

PIC16F87XA
40-Lead Plastic Dual In-line (P) – 600 mil (PDIP)
α
p
B1
B
A
A1
Units INCHES* MILLIMETERS
A2
2
1
D
c
Dimension Limits MIN NOM MAX MIN NOM MAX
n
E1
β
E
eB
Number of Pins n 40 40
Pitch p .100 2.54
L
Top to Seating Plane A .160 .175 .190 4.06 4.45 4.83
Molded Package Thickness A2 .140 .150 .160 3.56 3.81 4.06
Base to Seating Plane A1 .015 0.38
Shoulder to Shoulder Width E .595 .600 .625 15.11 15.24 15.88
Molded Package Width E1 .530 .545 .560 13.46 13.84 14.22
Overall Length D 2.045 2.058 2.065 51.94 52.26 52.45
Tip to Seating Plane L .120 .130 .135 3.05 3.30 3.43
Lead Thickness c .008 .012 .015 0.20 0.29 0.38
Upper Lead Width B1 .030 .050 .070 0.76 1.27 1.78
Lower Lead Width B .014 .018 .022 0.36 0.46 0.56
Overall Row Spacing § eB .620 .650 .680 15.75 16.51 17.27
Mold Draft Angle Top α 5 10 15 5 10 15
Mold Draft Angle Bottom β 5 10 15 5 10 15
* Controlling Parameter
§ Significant Characteristic
Notes:
Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed
.010” (0.254mm) per side.
JEDEC Equivalent: MO-011
Drawing No. C04-016

PIC16F87XA
44-Lead Plastic Thin Quad Flatpack (PT) 10x10x1 mm Body, 1.0/0.10 mm Lead Form (TQFP)
CH x 45 °
A1 A2
(F)
A
E
E1
#leads=n1
p
B
D1 D
n
1 2
φ
c
β
L
Units INCHES MILLIMETERS*
Pitch p .031 0.80
Pins per Side n1 11 11
Overall Height A .039 .043 .047 1.00 1.10 1.20
Standoff § A1 .002 .004 .006 0.05 0.10 0.15
Foot Length L .018 .024 .030 0.45 0.60 0.75
Footprint (Reference) (F) .039 1.00
α
Foot Angle φ 0 3.5 7 0 3.5 7
Overall Width E .463 .472 .482 11.75 12.00 12.25
Overall Length D .463 .472 .482 11.75 12.00 12.25
Molded Package Length D1 .390 .394 .398 9.90 10.00 10.10
Lead Thickness c .004 .006 .008 0.09 0.15 0.20
Lead Width B .012 .015 .017 0.30 0.38 0.44
Pin 1 Corner Chamfer CH .025 .035 .045 0.64 0.89 1.14
Notes:
Dimensions D1 and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed
.010” (0.254mm) per side.
JEDEC Equivalent: MS-026
Drawing No. C04-076

PIC16F87XA
44-Lead Plastic Leaded Chip Carrier (L) – Square (PLCC)
E
E1
#leads=n1
2
n
1
CH2 x 45° CH1 x 45°
β
D1 D
A2
p
A3
35° A
B1
B
D2
A1
E2
α
c
Pitch p .050 1.27
Pins per Side n1 11 11
Overall Height A .165 .173 .180 4.19 4.39 4.57
Molded Package Thickness A2
.145 .153 .160 3.68 3.87 4.06
Standoff § A1 .020 0.51
.028 .035 0.71 0.89
Side 1 Chamfer Height A3 .024 .029 .034 0.61 0.74 0.86
Corner Chamfer 1 CH1 .040 .045 .050 1.02 1.14 1.27
Corner Chamfer (others) CH2 .000 .005 .010 0.00 0.13 0.25
Overall Width E .685 .690 .695 17.40 17.53 17.65
Overall Length D .685 .690 .695 17.40 17.53 17.65
Molded Package Length D1 .650 .653 .656 16.51 16.59 16.66
Footprint Width E2 .590 .620 .630 14.99 15.75 16.00
Footprint Length D2 .590 .620 .630 14.99 15.75 16.00
Lead Thickness c .008 .011 .013 0.20 0.27 0.33
B .013 .020 .021 0.33 0.51 0.53
Lower Lead Width
Notes:
.010” (0.254mm) per side.
Drawing No. C04-048

PIC16F87XA
44-Lead Plastic Quad Flat No Lead Package (ML) 8x8 mm Body (QFN)
A1
Number of Pins
Pitch
Overall Height
Standoff
D D2
L
E2
EXPOSED
METAL
PAD
BOTTOM VIEW
PIN 1
INDEX ON
OPTIONAL PIN 1
INDEX ON
TOP MARKING EXPOSED PAD
.035 0.90
.001 0.02
A3
A
E
TOP VIEW
n
2
1
.031 0.80
Base Thickness A3 .010 REF 0.25 REF
Overall Width
Exposed Pad Width
Overall Length
p
B
.262 .268 .274 6.65 6.80 6.95
Exposed Pad Length .262 .268 .274 6.65 6.80 6.95
Lead Width
E2
D2
Lead Length L .014 .016 .018 0.35 0.40 0.45
*Controlling Parameter
MAX
Units
Dimension Limits
n
p
A
A1
E
D
INCHES
MILLIMETERS*
MIN
NOM MAX
44
.026 BSC
.315 BSC
MIN
.000
.039
.002 0
44
NOM
0.65 BSC
8.00 BSC
1.00
0.05
.315 BSC 8.00 BSC
B .012 .013 .013 0.30 0.33 0.35
Notes:
Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not
exceed .010" (0.254mm) per side.
JEDEC equivalent: M0-220
Drawing No. C04-103

PIC16F87XA
28-Lead Skinny Plastic Dual In-line (SP) – 300 mil (PDIP)
α
p
A2
B1
B
A
A1
2
1
D
c
L
n
E1
E
eB
β
Pitch p .100 2.54
Top to Seating Plane A .140 .150 .160 3.56 3.81 4.06
Base to Seating Plane A1 .015 0.38
Shoulder to Shoulder Width E .300 .310 .325 7.62 7.87 8.26
Overall Length D 1.345 1.365 1.385 34.16 34.67 35.18
Tip to Seating Plane L .125 .130 .135 3.18 3.30 3.43
Lead Thickness c .008 .012 .015 0.20 0.29 0.38
Lower Lead Width B .016 .019 .022 0.41 0.48 0.56
Overall Row Spacing § eB .320 .350 .430 8.13 8.89 10.92
Notes:
Dimension D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed
.010” (0.254mm) per side.
Drawing No. C04-070

PIC16F87XA
28-Lead Plastic Small Outline (SO) – Wide, 300 mil (SOIC)
2
1
D
L
φ
α
A
A1
E
E1
h
A2
p
n
B
c
β
45°
Pitch p .050 1.27
Overall Height A .093 .099 .104 2.36 2.50 2.64
Standoff § A1 .004 .008 .012 0.10 0.20 0.30
Overall Width E .394 .407 .420 10.01 10.34 10.67
Overall Length D .695 .704 .712 17.65 17.87 18.08
Chamfer Distance h .010 .020 .029 0.25 0.50 0.74
Foot Length L .016 .033 .050 0.41 0.84 1.27
Foot Angle Top φ 0 4 8 0 4 8
Lead Thickness c .009 .011 .013 0.23 0.28 0.33
Lead Width B .014 .017 .020 0.36 0.42 0.51
Notes:
.010” (0.254mm) per side.
Drawing No. C04-052

PIC16F87XA
28-Lead Plastic Shrink Small Outline (SS) – 209 mil, 5.30 mm (SSOP)
2
1
D
φ
β L
A1
A
Units INCHES MILLIMETERS*
E
E1
α
A2
p
n
B
c
Pitch p .026 0.65
Overall Height A .068 .073 .078 1.73 1.85 1.98
Standoff § A1 .002 .006 .010 0.05 0.15 0.25
Overall Width E .299 .309 .319 7.59 7.85 8.10
Overall Length D .396 .402 .407 10.06 10.20 10.34
Foot Length L .022 .030 .037 0.56 0.75 0.94
Lead Thickness c .004 .007 .010 0.10 0.18 0.25
Foot Angle φ 0 4 8 0.00 101.60 203.20
Lead Width B .010 .013 .015 0.25 0.32 0.38
β
Mold Draft Angle Bottom 0 5 10 0 5 10
Notes:
.010” (0.254mm) per side.
Drawing No. C04-073

PIC16F87XA
28-Lead Plastic Quad Flat No Lead Package (ML) 6x6 mm Body, Punch Singulated (QFN)
A1
CH X 45°
α
Number of Pins
Pitch
Overall Height
E
E1
n
R
D2
E2
TOP VIEW BOTTOM VIEW
Dimension Limits
Molded Package Thickness
Standoff
EXPOSED
METAL
PADS
L
.033 0.85
.0004 0.01
D
2
1
D1
A2 A
A3
Base Thickness A3 .008 REF 0.20 REF
Overall Width
Molded Package Width
Exposed Pad Width
Overall Length
Molded Package Length
Q
p
B
.140 .146 .152 3.55 3.70 3.85
Exposed Pad Length .140 .146 .152 3.55 3.70 3.85
Lead Width
Lead Length
Tie Bar Width
E2
D2
Tie Bar Length Q .012 .016 .026 0.30 0.40 0.65
Chamfer CH .009 .017 .024 0.24 0.42 0.60
Mold Draft Angle Top
*Controlling Parameter
Notes:
Units
n
p
A
A2
A1
E
E1
D
D1
B
L .020 .024 .030 0.50 0.60 0.75
R .005 .007 .010 0.13 0.17 0.23
α
MIN
.000
.009
MAX
INCHES
MILLIMETERS*
MIN
NOM MAX
28
.026 BSC
.026
.236 BSC
.226 BSC
.039
28
NOM
0.65 BSC
.031 0.65
.002 0.00
.236 BSC
.226 BSC
.011 .014 0.23
12°
6.00 BSC
5.75 BSC
1.00
0.80
0.05
6.00 BSC
5.75 BSC
0.28 0.35
Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not
exceed .010" (0.254mm) per side.
JEDEC equivalent: mMO-220
Drawing No. C04-114
12°

PIC16F87XA
APPENDIX A: REVISION HISTORY
Revision A (November 2001)
Original data sheet for PIC16F87XA devices. The
devices presented are enhanced versions of the
PIC16F87X microcontrollers discussed in the
“PIC16F87X Data Sheet” (DS30292).
Revision B (October 2003)
This revision includes the DC and AC Characteristics
Graphs and Tables. The Electrical Specifications in
Section 17.0 “Electrical Characteristics” have been
updated and there have been minor corrections to the
data sheet text.
APPENDIX B: DEVICE
DIFFERENCES
The differences between the devices in this data sheet
are listed in Table B-1.
TABLE B-1: DIFFERENCES BETWEEN DEVICES IN THE PIC16F87XA FAMILY
PIC16F873A PIC16F874A PIC16F876A PIC16F877A
(14-bit words)
4K 4K 8K 8K
Data Memory (bytes) 192 192 368 368
EEPROM Data Memory (bytes) 128 128 256 256
Interrupts 14 15 14 15
I/O Ports Ports A, B, C Ports A, B, C, D, E Ports A, B, C Ports A, B, C, D, E
Serial Communications MSSP, USART MSSP, USART MSSP, USART MSSP, USART
Parallel Slave Port No Yes No Yes
10-bit Analog-to-Digital Module 5 input channels 8 input channels 5 input channels 8 input channels
Packages 28-pin PDIP
28-pin SOIC
28-pin SSOP
28-pin QFN
40-pin PDIP
44-pin PLCC
44-pin TQFP
44-pin QFN
28-pin PDIP
28-pin SOIC
28-pin SSOP
28-pin QFN
40-pin PDIP
44-pin PLCC
44-pin TQFP
44-pin QFN

PIC16F87XA
APPENDIX C: CONVERSION
CONSIDERATIONS
Considerations for converting from previous versions
of devices to the ones listed in this data sheet are listed
in Table C-1.
TABLE C-1: CONVERSION CONSIDERATIONS
Characteristic PIC16C7X PIC16F87X PIC16F87XA
Pins 28/40 28/40 28/40
Timers 3 3 3
Interrupts 11 or 12 13 or 14 14 or 15
Communication PSP, USART, SSP
(SPI, I2C Slave)
PSP, USART, SSP
(SPI, I2C Master/Slave)
PSP, USART, SSP
(SPI, I2C Master/Slave)
Frequency 20 MHz 20 MHz 20 MHz
Voltage 2.5V-5.5V 2.2V-5.5V 2.0V-5.5V
A/D 8-bit,
4 conversion clock selects
10-bit,
10-bit,
CCP 2 2 2
Comparator — — 2
Comparator Voltage
Reference
— — Yes
Program Memory 4K, 8K EPROM 4K, 8K Flash
(Erase/Write on
single-word)
4K, 8K Flash
(Erase/Write on
four-word blocks)
RAM 192, 368 bytes 192, 368 bytes 192, 368 bytes
EEPROM Data None 128, 256 bytes 128, 256 bytes
Code Protection On/Off Segmented, starting at end
of program memory
On/Off
Program Memory
Write Protection
— On/Off Segmented, starting at
beginning of
program memory
Other  In-Circuit Debugger,
Low-Voltage Programming
In-Circuit Debugger,
Low-Voltage Programming

PIC16F87XA
INDEX
A
A/D ................................................................................... 127
Acquisition Requirements ........................................ 130
ADCON0 Register .................................................... 127
ADCON1 Register .................................................... 127
ADIF Bit .................................................................... 129
ADRESH Register .................................................... 127
ADRESL Register .................................................... 127
Analog Port Pins .................................................. 49, 51
Associated Registers and Bits ................................. 133
Calculating Acquisition Time .................................... 130
Configuring Analog Port Pins ................................... 131
Configuring the Interrupt .......................................... 129
Configuring the Module ............................................ 129
Conversion Clock ..................................................... 131
Conversions ............................................................. 132
Converter Characteristics ........................................ 194
Effects of a Reset ..................................................... 133
GO/DONE Bit ........................................................... 129
Internal Sampling Switch (Rss) Impedance ............. 130
Operation During Sleep ........................................... 133
Result Registers ....................................................... 132
Source Impedance ................................................... 130
A/D Conversion Requirements ......................................... 195
Absolute Maximum Ratings ............................................. 173
ACKSTAT ......................................................................... 101
ADCON0 Register .............................................................. 19
ADCON1 Register .............................................................. 20
Addressable Universal Synchronous Asynchronous
Receiver Transmitter. See USART.
ADRESH Register .............................................................. 19
ADRESL Register .............................................................. 20
Analog-to-Digital Converter. See A/D.
Application Notes
AN552 (Implementing Wake-up
on Key Stroke) ................................................... 44
AN556 (Implementing a Table Read) ........................ 30
Assembler
MPASM Assembler .................................................. 167
Asynchronous Reception
Associated Registers ....................................... 118, 120
Asynchronous Transmission
Associated Registers ............................................... 116
B
Banking, Data Memory ................................................. 16, 22
Baud Rate Generator ......................................................... 97
Associated Registers ............................................... 113
BCLIF ................................................................................. 28
BF ..................................................................................... 101
Block Diagrams
A/D ........................................................................... 129
Analog Input Model .......................................... 130, 139
Baud Rate Generator ................................................. 97
Capture Mode Operation ........................................... 65
Comparator I/O Operating Modes ............................ 136
Comparator Output .................................................. 138
Comparator Voltage Reference ............................... 142
Compare Mode Operation ......................................... 66
Crystal/Ceramic Resonator Operation
(HS, XT or LP Osc Configuration) .................... 145
External Clock Input Operation
(HS, XT or LP Osc Configuration) .................... 145
Interrupt Logic .......................................................... 153
MSSP (I2C Mode) ...................................................... 80
MSSP (SPI Mode) ..................................................... 71
On-Chip Reset Circuit .............................................. 147
PIC16F873A/PIC16F876A Architecture ...................... 6
PIC16F874A/PIC16F877A Architecture ...................... 7
PORTC
Peripheral Output Override
(RC2:0, RC7:5) Pins .................................. 46
Peripheral Output Override (RC4:3) Pins .......... 46
PORTD (in I/O Port Mode) ......................................... 48
PORTD and PORTE (Parallel Slave Port) ................. 51
PORTE (In I/O Port Mode) ......................................... 49
RA3:RA0 Pins ............................................................ 41
RA4/T0CKI Pin .......................................................... 42
RA5 Pin ..................................................................... 42
RB3:RB0 Pins ............................................................ 44
RB7:RB4 Pins ............................................................ 44
RC Oscillator Mode .................................................. 146
Recommended MCLR Circuit .................................. 148
Simplified PWM Mode ............................................... 67
Timer0/WDT Prescaler .............................................. 53
Timer1 ....................................................................... 58
Timer2 ....................................................................... 61
USART Receive ................................................117, 119
USART Transmit ...................................................... 115
Watchdog Timer ...................................................... 155
BOR. See Brown-out Reset.
BRG. See Baud Rate Generator.
BRGH Bit ......................................................................... 113
Brown-out Reset (BOR) .................... 143, 147, 148, 149, 150
BOR Status (BOR Bit) ............................................... 29
Bus Collision During a Repeated Start Condition ............ 108
Bus Collision During a Start Condition ............................. 106
Bus Collision During a Stop Condition ............................. 109
Bus Collision Interrupt Flag bit, BCLIF ............................... 28
C
C Compilers
MPLAB C17 ............................................................. 168
MPLAB C18 ............................................................. 168
MPLAB C30 ............................................................. 168
Capture/Compare/PWM (CCP) ......................................... 63
Associated Registers
Capture, Compare and Timer1 .......................... 68
PWM and Timer2 ............................................... 69
Capture Mode ............................................................ 65
CCP1IF .............................................................. 65
Prescaler ........................................................... 65
CCP Timer Resources ............................................... 63
Compare
Special Event Trigger Output of CCP1 .............. 66
Special Event Trigger Output of CCP2 .............. 66
Compare Mode .......................................................... 66
Software Interrupt Mode .................................... 66
Special Event Trigger ........................................ 66
Interaction of Two CCP Modules (table) .................... 63
PWM Mode ................................................................ 67
Duty Cycle ......................................................... 67
Example Frequencies/Resolutions (table) ......... 68
PWM Period ...................................................... 67
Special Event Trigger and A/D Conversions ............. 66

PIC16F87XA
Capture/Compare/PWM Requirements
(CCP1 and CCP2) .................................................... 186
CCP. See Capture/Compare/PWM.
CCP1CON Register ........................................................... 19
CCP2CON Register ........................................................... 19
CCPR1H Register ........................................................ 19, 63
CCPR1L Register ......................................................... 19, 63
CCPR2H Register ........................................................ 19, 63
CCPR2L Register ......................................................... 19, 63
CCPxM0 Bit ........................................................................64
CCPxM1 Bit ........................................................................64
CCPxM2 Bit ........................................................................64
CCPxM3 Bit ........................................................................64
CCPxX Bit ..........................................................................64
CCPxY Bit ..........................................................................64
CLKO and I/O Timing Requirements ............................... 183
CMCON Register ............................................................... 20
Code Examples
Call of a Subroutine in Page 1 from Page 0 ............... 30
Indirect Addressing .................................................... 31
Initializing PORTA ...................................................... 41
Loading the SSPBUF (SSPSR) Register ................... 74
Reading Data EEPROM ............................................. 35
Reading Flash Program Memory ............................... 36
Saving Status, W and PCLATH Registers
in RAM ............................................................ 154
Writing to Data EEPROM ........................................... 35
Writing to Flash Program Memory ............................. 38
Code Protection ....................................................... 143, 157
Comparator Module ......................................................... 135
Analog Input Connection
Considerations .................................................139
Associated Registers ...............................................140
Configuration ............................................................ 136
Effects of a Reset ..................................................... 139
Interrupts .................................................................. 138
Operation ................................................................. 137
Operation During Sleep ............................................ 139
Outputs ..................................................................... 137
Reference ................................................................. 137
Response Time ........................................................ 137
Comparator Specifications ...............................................180
Comparator Voltage Reference ....................................... 141
Computed GOTO ............................................................... 30
Configuration Bits ............................................................. 143
Configuration Word .......................................................... 144
Conversion Considerations .............................................. 220
CVRCON Register ............................................................. 20
D
Data EEPROM and Flash Program Memory
EEADR Register ........................................................ 33
EEADRH Register ...................................................... 33
EECON1 Register ...................................................... 33
EECON2 Register ...................................................... 33
EEDATA Register ...................................................... 33
EEDATH Register ...................................................... 33
Data EEPROM Memory
Associated Registers ................................................. 39
EEADR Register ........................................................ 33
EEADRH Register ..................................................... 33
EECON1 Register ...................................................... 33
EECON2 Register ...................................................... 33
Operation During Code-Protect ................................. 39
Protection Against Spurious Writes ........................... 39
Reading ..................................................................... 35
Write Complete Flag Bit (EEIF) ................................. 33
Writing ........................................................................ 35
Data Memory ..................................................................... 16
Bank Select (RP1:RP0 Bits) .................................16, 22
General Purpose Registers ....................................... 16
Register File Map ..................................................17, 18
Special Function Registers ........................................ 19
DC and AC Characteristics Graphs and Tables .............. 197
DC Characteristics ....................................................175–179
Demonstration Boards
PICDEM 1 ................................................................ 170
PICDEM 17 .............................................................. 170
PICDEM 18R PIC18C601/801 ................................. 171
PICDEM 2 Plus ........................................................ 170
PICDEM 3 PIC16C92X ............................................ 170
PICDEM 4 ................................................................ 170
PICDEM LIN PIC16C43X ........................................ 171
PICDEM USB PIC16C7X5 ...................................... 171
PICDEM.net Internet/Ethernet ................................. 170
Development Support ...................................................... 167
Device Differences ........................................................... 219
Device Overview .................................................................. 5
Direct Addressing ............................................................... 31
E
EEADR Register ...........................................................21, 33
EEADRH Register .........................................................21, 33
EECON1 Register .........................................................21, 33
EECON2 Register .........................................................21, 33
EEDATA Register .............................................................. 21
EEDATH Register .............................................................. 21
Electrical Characteristics .................................................. 173
Errata ................................................................................... 4
Evaluation and Programming Tools ................................. 171
External Clock Timing Requirements ............................... 182
External Interrupt Input (RB0/INT). See Interrupt Sources.
External Reference Signal ............................................... 137
F
Firmware Instructions ....................................................... 159
EECON1 Register ...................................................... 33
EECON2 Register ...................................................... 33
Reading ..................................................................... 36
Writing ........................................................................ 37
FSR Register ..........................................................19, 20, 31
G
General Call Address Support ........................................... 94

PIC16F87XA
I
I/O Ports ............................................................................. 41
I2C Bus Data Requirements ............................................ 192
I2C Bus Start/Stop Bits Requirements ............................. 191
I2C Mode
Registers .................................................................... 80
I2C Mode ............................................................................ 80
ACK Pulse ............................................................ 84, 85
Acknowledge Sequence Timing ............................... 104
Baud Rate Generator ................................................. 97
Bus Collision
Repeated Start Condition ................................. 108
Start Condition ................................................. 106
Stop Condition ................................................. 109
Clock Arbitration ......................................................... 98
Effect of a Reset ...................................................... 105
General Call Address Support ................................... 94
Master Mode .............................................................. 95
Operation ........................................................... 96
Repeated Start Timing ..................................... 100
Master Mode Reception ........................................... 101
Master Mode Start Condition ..................................... 99
Master Mode Transmission ...................................... 101
Multi-Master Communication, Bus Collision
and Arbitration .................................................. 105
Multi-Master Mode ................................................... 105
Read/Write Bit Information (R/W Bit) ................... 84, 85
Serial Clock (RC3/SCK/SCL) ..................................... 85
Slave Mode ................................................................ 84
Addressing ......................................................... 84
Reception ........................................................... 85
Transmission ...................................................... 85
Sleep Operation ....................................................... 105
Stop Condition Timing .............................................. 104
ID Locations ............................................................. 143, 157
In-Circuit Debugger .................................................. 143, 157
Resources ................................................................ 157
In-Circuit Serial Programming (ICSP) ...................... 143, 158
INDF Register .........................................................19, 20, 31
Indirect Addressing ............................................................ 31
FSR Register ............................................................. 16
Instruction Format ............................................................ 159
Instruction Set .................................................................. 159
ADDLW .................................................................... 161
ADDWF .................................................................... 161
ANDLW .................................................................... 161
ANDWF .................................................................... 161
BCF .......................................................................... 161
BSF .......................................................................... 161
BTFSC ..................................................................... 161
BTFSS ..................................................................... 161
CALL ........................................................................ 162
CLRF ........................................................................ 162
CLRW ...................................................................... 162
CLRWDT .................................................................. 162
COMF ...................................................................... 162
DECF ....................................................................... 162
DECFSZ ................................................................... 163
GOTO ...................................................................... 163
INCF ......................................................................... 163
INCFSZ .................................................................... 163
IORLW ..................................................................... 163
IORWF ..................................................................... 163
RETURN .................................................................. 164
RLF .......................................................................... 164
RRF ......................................................................... 164
SLEEP ..................................................................... 164
SUBLW .................................................................... 164
SUBWF .................................................................... 164
SWAPF .................................................................... 165
XORLW ................................................................... 165
XORWF ................................................................... 165
Summary Table ....................................................... 160
INT Interrupt (RB0/INT). See Interrupt Sources.
INTCON Register ............................................................... 24
GIE Bit ....................................................................... 24
INTE Bit ..................................................................... 24
INTF Bit ..................................................................... 24
PEIE Bit ..................................................................... 24
RBIE Bit ..................................................................... 24
RBIF Bit ................................................................24, 44
TMR0IE Bit ................................................................ 24
TMR0IF Bit ................................................................. 24
Inter-Integrated Circuit. See I2C.
Internal Reference Signal ................................................ 137
Internal Sampling Switch (Rss) Impedance ..................... 130
Interrupt Sources ......................................................143, 153
Interrupt-on-Change (RB7:RB4) ................................ 44
RB0/INT Pin, External .....................................9, 11, 154
TMR0 Overflow ........................................................ 154
USART Receive/Transmit Complete ....................... 111
Interrupts
Bus Collision Interrupt ................................................ 28
Synchronous Serial Port Interrupt .............................. 26
Interrupts, Context Saving During .................................... 154
Interrupts, Enable Bits
Global Interrupt Enable (GIE Bit) ........................24, 153
Interrupt-on-Change (RB7:RB4)
Enable (RBIE Bit) .......................................24, 154
Peripheral Interrupt Enable (PEIE Bit) ....................... 24
RB0/INT Enable (INTE Bit) ........................................ 24
TMR0 Overflow Enable (TMR0IE Bit) ........................ 24
Interrupts, Flag Bits
Interrupt-on-Change (RB7:RB4) Flag
(RBIF Bit) ..............................................24, 44, 154
RB0/INT Flag (INTF Bit) ............................................ 24
TMR0 Overflow Flag (TMR0IF Bit) .....................24, 154
L
Loading of PC .................................................................... 30
Low-Voltage ICSP Programming ..................................... 158
Low-Voltage In-Circuit Serial Programming ..................... 143
M
Master Clear (MCLR) ........................................................... 8
MCLR Reset, Normal Operation ...............147, 149, 150
MCLR Reset, Sleep ..................................147, 149, 150
Master Synchronous Serial Port (MSSP). See MSSP.
MCLR ............................................................................... 148
MCLR/VPP ......................................................................... 10
Memory Organization ........................................................ 15
Data EEPROM Memory ............................................. 33
Data Memory ............................................................. 16
Flash Program Memory ............................................. 33
Program Memory ....................................................... 15
MPLAB ASM30 Assembler, Linker, Librarian .................. 168
MPLAB ICD 2 In-Circuit Debugger .................................. 169
MPLAB ICE 2000 High-Performance Universal
In-Circuit Emulator ................................................... 169

PIC16F87XA
MPLAB ICE 4000 High-Performance Universal
In-Circuit Emulator ...................................................169
MPLAB Integrated Development
Environment Software .............................................. 167
MPLINK Object Linker/MPLIB Object Librarian ............... 168
MSSP ................................................................................. 71
I2C Mode. See I2C.
SPI Mode ................................................................... 71
SPI Mode. See SPI.
MSSP Module
Clock Stretching ......................................................... 90
Clock Synchronization and the CKP Bit ..................... 91
Control Registers (General) ....................................... 71
Operation ................................................................... 84
Overview .................................................................... 71
SPI Master Mode ....................................................... 76
SPI Slave Mode ......................................................... 77
SSPBUF ..................................................................... 76
SSPSR ....................................................................... 76
Multi-Master Mode ........................................................... 105
O
Opcode Field Descriptions ...............................................159
OPTION_REG Register .....................................................23
INTEDG Bit ................................................................ 23
PS2:PS0 Bits .............................................................. 23
PSA Bit ....................................................................... 23
RBPU Bit .................................................................... 23
T0CS Bit ..................................................................... 23
T0SE Bit ..................................................................... 23
OSC1/CLKI Pin .............................................................. 8, 10
OSC2/CLKO Pin ............................................................ 8, 10
Oscillator Configuration
HS .................................................................... 145, 149
LP ..................................................................... 145, 149
RC ............................................................ 145, 146, 149
XT ..................................................................... 145, 149
Oscillator Selection .......................................................... 143
Oscillator Start-up Timer (OST) ............................... 143, 148
Oscillator, WDT ................................................................ 155
Oscillators
Capacitor Selection .................................................. 146
Ceramic Resonator Selection .................................. 145
Crystal and Ceramic Resonators ............................. 145
RC ............................................................................ 146
P
Package Information
Marking ....................................................................209
Packaging Information ..................................................... 209
Paging, Program Memory .................................................. 30
Parallel Slave Port (PSP) ....................................... 13, 48, 51
Associated Registers .................................................52
RE0/RD/AN5 Pin .................................................. 49, 51
RE1/WR/AN6 Pin ................................................. 49, 51
RE2/CS/AN7 Pin .................................................. 49, 51
Select (PSPMODE Bit) ..............................48, 49, 50, 51
Parallel Slave Port Requirements
(PIC16F874A/ 877A Only) ....................................... 187
PCL Register .......................................................... 19, 20, 30
PCLATH Register ................................................... 19, 20, 30
PCON Register .................................................... 20, 29, 149
BOR Bit ......................................................................29
POR Bit ......................................................................29
PIC16F87XA Product Identification System ..................... 231
PICkit 1 Flash Starter Kit .................................................. 171
PICSTART Plus Development Programmer .................... 169
PIE1 Register ................................................................20, 25
PIE2 Register ................................................................20, 27
Pinout Descriptions
PIC16F873A/PIC16F876A ........................................... 8
PIR1 Register ...............................................................19, 26
PIR2 Register ...............................................................19, 28
POP ................................................................................... 30
POR. See Power-on Reset.
PORTA ...........................................................................8, 10
Functions ................................................................... 43
PORTA Register ...................................................19, 41
TRISA Register .......................................................... 41
PORTB ...........................................................................9, 11
Functions ................................................................... 45
PORTB Register ...................................................19, 44
Pull-up Enable (RBPU Bit) ......................................... 23
RB0/INT Edge Select (INTEDG Bit) .......................... 23
RB0/INT Pin, External .....................................9, 11, 154
RB7:RB4 Interrupt-on-Change ................................ 154
RB7:RB4 Interrupt-on-Change Enable
(RBIE Bit) ....................................................24, 154
RB7:RB4 Interrupt-on-Change Flag
(RBIF Bit) ..............................................24, 44, 154
TRISB Register .....................................................21, 44
PORTB Register ................................................................ 21
PORTC ...........................................................................9, 12
Functions ................................................................... 47
PORTC Register ...................................................19, 46
RC3/SCK/SCL Pin ..................................................... 85
RC6/TX/CK Pin ........................................................ 112
RC7/RX/DT Pin .................................................112, 113
TRISC Register ...................................................46, 111
PORTD .........................................................................13, 51
Functions ................................................................... 48
Parallel Slave Port (PSP) Function ............................ 48
PORTD Register ...................................................19, 48
TRISD Register .......................................................... 48
PORTE .............................................................................. 13
Analog Port Pins ...................................................49, 51
Functions ................................................................... 49
Input Buffer Full Status (IBF Bit) ................................ 50
Input Buffer Overflow (IBOV Bit) ................................ 50
Output Buffer Full Status (OBF Bit) ........................... 50
PORTE Register ...................................................19, 49
PSP Mode Select (PSPMODE Bit) ........... 48, 49, 50, 51
RE0/RD/AN5 Pin ..................................................49, 51
RE1/WR/AN6 Pin ..................................................49, 51
RE2/CS/AN7 Pin ...................................................49, 51
TRISE Register .......................................................... 49
Postscaler, WDT
Assignment (PSA Bit) ................................................ 23
Rate Select (PS2:PS0 Bits) ....................................... 23
Power-down Mode. See Sleep.
Power-on Reset (POR) ..................... 143, 147, 148, 149, 150
POR Status (POR Bit) ............................................... 29
Power Control (PCON) Register .............................. 149
Power-down (PD Bit) ..........................................22, 147
Power-up Timer (PWRT) ......................................... 143
Time-out (TO Bit) ................................................22, 147

PIC16F87XA
Power-up Timer (PWRT) .................................................. 148
PR2 Register ................................................................ 20, 61
Prescaler, Timer0
Assignment (PSA Bit) ................................................ 23
Rate Select (PS2:PS0 Bits) ....................................... 23
PRO MATE II Universal Device Programmer .................. 169
Program Counter
Reset Conditions ...................................................... 149
Program Memory ............................................................... 15
Interrupt Vector .......................................................... 15
Paging ........................................................................ 30
Program Memory Map and Stack
(PIC16F873A/874A) ........................................... 15
Program Memory Map and Stack
(PIC16F876A/877A) ........................................... 15
Reset Vector .............................................................. 15
Program Verification ......................................................... 157
Programming Pin (VPP) ........................................................ 8
Programming, Device Instructions ................................... 159
PSP. See Parallel Slave Port.
Pulse Width Modulation. See Capture/Compare/PWM,
PWM Mode.
PUSH ................................................................................. 30
R
RA0/AN0 Pin .................................................................. 8, 10
RA1/AN1 Pin .................................................................. 8, 10
RA2/AN2/VREF-/CVREF Pin ............................................ 8, 10
RA3/AN3/VREF+ Pin ....................................................... 8, 10
RA4/T0CKI/C1OUT Pin .................................................. 8, 10
RA5/AN4/SS/C2OUT Pin ............................................... 8, 10
RAM. See Data Memory.
RB0/INT Pin ................................................................... 9, 11
RB1 Pin .......................................................................... 9, 11
RB2 Pin .......................................................................... 9, 11
RB3/PGM Pin ................................................................. 9, 11
RB4 Pin .......................................................................... 9, 11
RB5 Pin .......................................................................... 9, 11
RB6/PGC Pin ................................................................. 9, 11
RB7/PGD Pin ................................................................. 9, 11
RC0/T1OSO/T1CKI Pin ................................................. 9, 12
RC1/T1OSI/CCP2 Pin .................................................... 9, 12
RC2/CCP1 Pin ............................................................... 9, 12
RC3/SCK/SCL Pin ......................................................... 9, 12
RC4/SDI/SDA Pin .......................................................... 9, 12
RC5/SDO Pin ................................................................. 9, 12
RC6/TX/CK Pin .............................................................. 9, 12
RC7/RX/DT Pin .............................................................. 9, 12
RCREG Register ................................................................ 19
RCSTA Register ................................................................. 19
ADDEN Bit ............................................................... 112
CREN Bit .................................................................. 112
FERR Bit .................................................................. 112
OERR Bit ................................................................. 112
RX9 Bit ..................................................................... 112
RX9D Bit .................................................................. 112
SPEN Bit .......................................................... 111, 112
SREN Bit .................................................................. 112
RD0/PSP0 Pin .................................................................... 13
RD1/PSP1 Pin .................................................................... 13
RD2/PSP2 Pin .................................................................... 13
RD3/PSP3 Pin .................................................................... 13
RD4/PSP4 Pin .................................................................... 13
RD5/PSP5 Pin .................................................................... 13
RD6/PSP6 Pin .................................................................... 13
RD7/PSP7 Pin .................................................................... 13
RE0/RD/AN5 Pin ............................................................... 13
RE1/WR/AN6 Pin ............................................................... 13
RE2/CS/AN7 Pin ................................................................ 13
Read-Modify-Write Operations ........................................ 159
Register File ....................................................................... 16
Register File Map (PIC16F873A/874A) ............................. 18
Register File Map (PIC16F876A/877A) ............................. 17
Registers
ADCON0 (A/D Control 0) ......................................... 127
ADCON1 (A/D Control 1) ......................................... 128
CCP1CON/CCP2CON (CCP Control 1
and CCP Control 2) ........................................... 64
CMCON (Comparator Control) ................................ 135
CVRCON (Comparator Voltage
Reference Control) .......................................... 141
EECON1 (EEPROM Control 1) ................................. 34
FSR ........................................................................... 31
INTCON ..................................................................... 24
OPTION_REG ......................................................23, 54
PCON (Power Control) .............................................. 29
PIE1 (Peripheral Interrupt Enable 1) .......................... 25
PIE2 (Peripheral Interrupt Enable 2) .......................... 27
PIR1 (Peripheral Interrupt Request 1) ....................... 26
PIR2 (Peripheral Interrupt Request 2) ....................... 28
RCSTA (Receive Status and Control) ..................... 112
Special Function, Summary ....................................... 19
SSPCON (MSSP Control 1, I2C Mode) ..................... 82
SSPCON (MSSP Control 1, SPI Mode) ..................... 73
SSPCON2 (MSSP Control 2, I2C Mode) ................... 83
SSPSTAT (MSSP Status, I2C Mode) ........................ 81
SSPSTAT (MSSP Status, SPI Mode) ........................ 72
Status ........................................................................ 22
T1CON (Timer1 Control) ........................................... 57
T2CON (Timer2 Control) ........................................... 61
TRISE Register .......................................................... 50
TXSTA (Transmit Status and Control) ..................... 111
Reset ........................................................................143, 147
Brown-out Reset (BOR). See Brown-out Reset (BOR).
MCLR Reset. See MCLR.
Power-on Reset (POR). See Power-on Reset (POR).
Reset Conditions for PCON Register ...................... 149
Reset Conditions for Program Counter .................... 149
Reset Conditions for Status Register ....................... 149
WDT Reset. See Watchdog Timer (WDT).
Reset, Watchdog Timer, Oscillator Start-up Timer,
Power-up Timer and Brown-out Reset
Requirements .......................................................... 184
Revision History ............................................................... 219
S
SCI. See USART.
SCK ................................................................................... 71
SDI ..................................................................................... 71
SDO ................................................................................... 71
Serial Clock, SCK .............................................................. 71
Serial Communication Interface. See USART.
Serial Data In, SDI ............................................................. 71
Serial Data Out, SDO ........................................................ 71
Serial Peripheral Interface. See SPI.
Slave Select Synchronization ............................................ 77
Slave Select, SS ................................................................ 71
Sleep .................................................................143, 147, 156
Software Simulator (MPLAB SIM) ................................... 168
Software Simulator (MPLAB SIM30) ............................... 168
SPBRG Register ................................................................ 20
Special Features of the CPU ........................................... 143

PIC16F87XA
Special Function Registers ................................................ 19
Special Function Registers (SFRs) .................................... 19
Speed, Operating ................................................................. 1
SPI Mode ..................................................................... 71, 77
Associated Registers .................................................79
Bus Mode Compatibility ............................................. 79
Effects of a Reset ....................................................... 79
Enabling SPI I/O ......................................................... 75
Master Mode .............................................................. 76
Master/Slave Connection ........................................... 75
Serial Clock ................................................................ 71
Serial Data In ............................................................. 71
Serial Data Out ........................................................... 71
Slave Select ............................................................... 71
Slave Select Synchronization ..................................... 77
Sleep Operation ......................................................... 79
SPI Clock ................................................................... 76
Typical Connection .....................................................75
SPI Mode Requirements .................................................. 190
SS ...................................................................................... 71
SSP
SPI Master/Slave Connection .................................... 75
SSPADD Register .............................................................. 20
SSPBUF Register .............................................................. 19
SSPCON Register .............................................................. 19
SSPCON2 Register ............................................................ 20
SSPIF ................................................................................. 26
SSPOV ............................................................................. 101
SSPSTAT Register ............................................................ 20
R/W Bit ................................................................. 84, 85
Stack .................................................................................. 30
Overflows ................................................................... 30
Underflow ................................................................... 30
Status Register
C Bit ........................................................................... 22
DC Bit ......................................................................... 22
IRP Bit ........................................................................22
PD Bit ................................................................. 22, 147
RP1:RP0 Bits ............................................................. 22
TO Bit ................................................................. 22, 147
Z Bit ............................................................................ 22
Synchronous Master Reception
Synchronous Master Transmission
Synchronous Serial Port Interrupt ...................................... 26
Synchronous Slave Reception
Synchronous Slave Transmission
T
T1CKPS0 Bit ......................................................................57
T1CKPS1 Bit ......................................................................57
T1CON Register ................................................................. 19
T1OSCEN Bit ..................................................................... 57
T1SYNC Bit ........................................................................57
T2CKPS0 Bit ......................................................................61
T2CKPS1 Bit ......................................................................61
T2CON Register ................................................................. 19
TAD ................................................................................... 131
Time-out Sequence .......................................................... 148
Timer0 ................................................................................ 53
Clock Source Edge Select (T0SE Bit) ....................... 23
Clock Source Select (T0CS Bit) ................................. 23
External Clock ............................................................ 54
Interrupt ..................................................................... 53
Overflow Enable (TMR0IE Bit) ................................... 24
Overflow Flag (TMR0IF Bit) ................................24, 154
Overflow Interrupt .................................................... 154
Prescaler .................................................................... 54
T0CKI ......................................................................... 54
Timer0 and Timer1 External Clock Requirements ........... 185
Timer1 ................................................................................ 57
Asynchronous Counter Mode .................................... 59
Reading and Writing to ...................................... 59
Counter Operation ..................................................... 58
Operation in Timer Mode ........................................... 58
Oscillator .................................................................... 59
Capacitor Selection ............................................ 59
Prescaler .................................................................... 60
Resetting of Timer1 Registers ................................... 60
Resetting Timer1 Using a CCP Trigger Output ......... 59
Synchronized Counter Mode ..................................... 58
TMR1H ...................................................................... 59
TMR1L ....................................................................... 59
Timer2 ................................................................................ 61
Output ........................................................................ 62
Postscaler .................................................................. 61
Prescaler .................................................................... 61
Prescaler and Postscaler ........................................... 62
Timing Diagrams
A/D Conversion ........................................................ 195
Acknowledge Sequence .......................................... 104
Asynchronous Master Transmission ........................ 116
Asynchronous Master Transmission
(Back to Back) ................................................. 116
Asynchronous Reception ......................................... 118
Asynchronous Reception with
Address Byte First ........................................... 120
Asynchronous Reception with
Address Detect ................................................ 120
Baud Rate Generator with Clock Arbitration .............. 98
BRG Reset Due to SDA Arbitration During
Start Condition ................................................. 107
Brown-out Reset ...................................................... 184
Bus Collision During a Repeated
Start Condition (Case 1) .................................. 108
Bus Collision During Repeated
Start Condition (Case 2) .................................. 108
Bus Collision During Start Condition
(SCL = 0) ......................................................... 107
Bus Collision During Start Condition
(SDA Only) ....................................................... 106
Bus Collision During Stop Condition
(Case 1) ........................................................... 109
Bus Collision During Stop Condition
(Case 2) ........................................................... 109
Bus Collision for Transmit and Acknowledge .......... 105
Capture/Compare/PWM (CCP1 and CCP2) ............ 186
CLKO and I/O .......................................................... 183
Clock Synchronization ............................................... 91
External Clock .......................................................... 182
First Start Bit .............................................................. 99

PIC16F87XA
I2C Bus Data ............................................................ 191
I2C Bus Start/Stop Bits ............................................. 190
I2C Master Mode (Reception, 7-bit Address) ........... 103
I2C Master Mode (Transmission,
7 or 10-bit Address) ......................................... 102
I2C Slave Mode (Transmission, 10-bit Address) ........ 89
I2C Slave Mode (Transmission, 7-bit Address) .......... 87
I2C Slave Mode with SEN = 1 (Reception,
10-bit Address) ................................................... 93
10-bit Address) ................................................... 88
7-bit Address) ..................................................... 86
7-bit Address) ..................................................... 92
Parallel Slave Port (PIC16F874A/877A Only) .......... 187
Parallel Slave Port (PSP) Read ................................. 52
Parallel Slave Port (PSP) Write ................................. 52
Repeat Start Condition ............................................. 100
Reset, Watchdog Timer, Start-up Timer
and Power-up Timer ........................................ 184
Slave Mode General Call Address Sequence
(7 or 10-bit Address Mode) ................................ 94
Slave Synchronization ............................................... 77
Slow Rise Time (MCLR Tied to VDD via
RC Network) .................................................... 152
SPI Master Mode (CKE = 0, SMP = 0) .................... 188
SPI Master Mode (CKE = 1, SMP = 1) .................... 188
SPI Mode (Master Mode) ........................................... 76
SPI Mode (Slave Mode with CKE = 0) ....................... 78
SPI Mode (Slave Mode with CKE = 1) ....................... 78
SPI Slave Mode (CKE = 0) ...................................... 189
SPI Slave Mode (CKE = 1) ...................................... 189
Stop Condition Receive or Transmit Mode .............. 104
Synchronous Reception
(Master Mode, SREN) ...................................... 124
Synchronous Transmission ...................................... 122
Synchronous Transmission (Through TXEN) .......... 122
Time-out Sequence on Power-up
(MCLR Not Tied to VDD)
Case 1 .............................................................. 152
Case 2 .............................................................. 152
Time-out Sequence on Power-up (MCLR Tied
to VDD via RC Network) ................................... 151
Timer0 and Timer1 External Clock .......................... 185
USART Synchronous Receive
(Master/Slave) .................................................. 193
USART Synchronous Transmission
(Master/Slave) .................................................. 193
Wake-up from Sleep via Interrupt ............................ 157
Timing Parameter Symbology .......................................... 181
TMR0 Register ................................................................... 19
TMR1CS Bit ....................................................................... 57
TMR1H Register ................................................................ 19
TMR1L Register ................................................................. 19
TMR1ON Bit ....................................................................... 57
TMR2 Register ................................................................... 19
TMR2ON Bit ....................................................................... 61
TMRO Register .................................................................. 21
TOUTPS0 Bit ..................................................................... 61
TOUTPS1 Bit ..................................................................... 61
TOUTPS2 Bit ..................................................................... 61
TOUTPS3 Bit ..................................................................... 61
TRISA Register .................................................................. 20
TRISB Register .................................................................. 20
TRISC Register .................................................................. 20
TRISD Register .................................................................. 20
TRISE Register .................................................................. 20
IBF Bit ........................................................................ 50
IBOV Bit ..................................................................... 50
OBF Bit ...................................................................... 50
PSPMODE Bit ........................................... 48, 49, 50, 51
TXREG Register ................................................................ 19
TXSTA Register ................................................................. 20
BRGH Bit ................................................................. 111
CSRC Bit ................................................................. 111
SYNC Bit ................................................................. 111
TRMT Bit .................................................................. 111
TX9 Bit ..................................................................... 111
TX9D Bit .................................................................. 111
TXEN Bit .................................................................. 111
U
USART ............................................................................. 111
Address Detect Enable (ADDEN Bit) ....................... 112
Asynchronous Mode ................................................ 115
Asynchronous Receive (9-bit Mode) ........................ 119
Asynchronous Receive with Address Detect.
See Asynchronous Receive (9-bit Mode).
Asynchronous Receiver ........................................... 117
Asynchronous Reception ......................................... 118
Asynchronous Transmitter ....................................... 115
Baud Rate Generator (BRG) ................................... 113
Baud Rate Formula ......................................... 113
Baud Rates, Asynchronous Mode
(BRGH = 0) .............................................. 114
Baud Rates, Asynchronous Mode
(BRGH = 1) .............................................. 114
High Baud Rate Select (BRGH Bit) ................. 111
Sampling .......................................................... 113
Clock Source Select (CSRC Bit) .............................. 111
Continuous Receive Enable (CREN Bit) .................. 112
Framing Error (FERR Bit) ........................................ 112
Mode Select (SYNC Bit) .......................................... 111
Overrun Error (OERR Bit) ........................................ 112
Receive Data, 9th Bit (RX9D Bit) ............................. 112
Receive Enable, 9-bit (RX9 Bit) ............................... 112
Serial Port Enable (SPEN Bit) ..........................111, 112
Single Receive Enable (SREN Bit) .......................... 112
Synchronous Master Mode ...................................... 121
Synchronous Master Reception ............................... 123
Synchronous Master Transmission ......................... 121
Synchronous Slave Mode ........................................ 124
Synchronous Slave Reception ................................. 125
Synchronous Slave Transmit ................................... 124
Transmit Data, 9th Bit (TX9D) ................................. 111
Transmit Enable (TXEN Bit) .................................... 111
Transmit Enable, 9-bit (TX9 Bit) .............................. 111
Transmit Shift Register Status (TRMT Bit) .............. 111
USART Synchronous Receive Requirements ................. 193
V
VDD Pin ...........................................................................9, 13
Voltage Reference Specifications .................................... 180
VSS Pin ...........................................................................9, 13

PIC16F87XA
W
Wake-up from Sleep ................................................ 143, 156
Interrupts .......................................................... 149, 150
MCLR Reset ............................................................. 150
WDT Reset ............................................................... 150
Wake-up Using Interrupts ................................................ 156
Watchdog Timer
Register Summary ...................................................155
Watchdog Timer (WDT) ........................................... 143, 155
Enable (WDTE Bit) ...................................................155
Postscaler. See Postscaler, WDT.
Programming Considerations ................................... 155
RC Oscillator ............................................................ 155
Time-out Period ........................................................ 155
WDT Reset, Normal Operation ................ 147, 149, 150
WDT Reset, Sleep ................................... 147, 149, 150
WCOL ................................................................ 99, 101, 104
WCOL Status Flag ............................................................. 99
WWW, On-Line Support .......................................................4

PIC16F87XA
ON-LINE SUPPORT
Microchip provides on-line support on the Microchip
World Wide Web site.
The web site is used by Microchip as a means to make
files and information easily available to customers. To
view the site, the user must have access to the Internet
and a web browser, such as Netscape® or Microsoft®
Internet Explorer. Files are also available for FTP
download from our FTP site.
Connecting to the Microchip Internet
Web Site
The Microchip web site is available at the following
URL:
www.microchip.com
The file transfer site is available by using an FTP
service to connect to:
ftp://ftp.microchip.com
The web site and file transfer site provide a variety of
services. Users may download files for the latest
Development Tools, Data Sheets, Application Notes,
User's Guides, Articles and Sample Programs. A vari-ety
of Microchip specific business information is also
available, including listings of Microchip sales offices,
distributors and factory representatives. Other data
available for consideration is:
• Latest Microchip Press Releases
• Technical Support Section with Frequently Asked
Questions
• Design Tips
• Device Errata
• Job Postings
• Microchip Consultant Program Member Listing
• Links to other useful web sites related to
Microchip Products
• Conferences for products, Development Systems,
technical information and more
• Listing of seminars and events
SYSTEMS INFORMATION AND
UPGRADE HOT LINE
The Systems Information and Upgrade Line provides
system users a listing of the latest versions of all of
Microchip's development systems software products.
Plus, this line provides information on how customers
can receive the most current upgrade kits. The Hot Line
Numbers are:
1-800-755-2345 for U.S. and most of Canada, and
1-480-792-7302 for the rest of the world.
042003

PIC16F87XA
READER RESPONSE
It is our intention to provide you with the best documentation possible to ensure successful use of your Microchip prod-uct.
If you wish to provide your comments on organization, clarity, subject matter, and ways in which our documentation
can better serve you, please FAX your comments to the Technical Publications Manager at (480) 792-4150.
Please list the following information, and use this outline to provide us with your comments about this document.
To: Technical Publications Manager
RE: Reader Response
Total Pages Sent ________
From: Name
Company
Address
City / State / ZIP / Country
Telephone: (_______) _________ - _________
Application (optional):
Would you like a reply? Y N
Device: Literature Number:
Questions:
FAX: (______) _________ - _________
PIC16F87XA DS39582B
1. What are the best features of this document?
2. How does this document meet your hardware and software development needs?
3. Do you find the organization of this document easy to follow? If not, why?
4. What additions to the document do you think would enhance the structure and subject?
5. What deletions from the document could be made without affecting the overall usefulness?
6. Is there any incorrect or misleading information (what and where)?
7. How would you improve this document?

PIC16F87XA
PIC16F87XA PRODUCT IDENTIFICATION SYSTEM
To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.
PART NO. X /XX XXX
Temperature Package Pattern
Range
Device
Device PIC16F87XA(1), PIC16F87XAT(2); VDD range 4.0V to 5.5V
PIC16LF87XA(1), PIC16LF87XAT(2); VDD range 2.0V to 5.5V
Temperature Range I = -40°C to +85°C (Industrial)
Package ML = QFN (Metal Lead Frame)
PT = TQFP (Thin Quad Flatpack)
SO = SOIC
SP = Skinny Plastic DIP
P = PDIP
L = PLCC
S = SSOP
Examples:
a) PIC16F873A-I/P 301 = Industrial temp., PDIP
package, normal VDD limits, QTP pattern #301.
b) PIC16LF876A-I/SO = Industrial temp., SOIC
package, Extended VDD limits.
c) PIC16F877A-I/P = Industrial temp., PDIP package,
10 MHz, normal VDD limits.
Note 1: F = CMOS Flash
LF = Low-Power CMOS Flash
2: T = in tape and reel - SOIC, PLCC,
TQFP packages only

WORLDWIDE SALES AND SERVICE
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Tel: 86-765-8395507 Fax: 86-765-8395571
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82-2-558-5934
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Denmark
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Italy
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Netherlands
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Fax: 31-416-690340
United Kingdom
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Tel: 44-118-921-5869
Fax: 44-118-921-5820
07/28/03

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