8051 Architecture, System Bus, Advantages
- 1. YCCE, Nagpur MGI 8051 Microcontroller Dr. P. T. Karule Professor Department of Electronics Engineering Yeshwantrao Chavan College of Engineering, Nagpur (M. S.) Email: ptkarule@gmail.com, 412@ycce.in Website: www.ycce.edu 8051 Microcontroller
- 2. 12/9/2024 2 Microprocessor Based System • CPU is Microprocessor • Memory (RAM, ROM), Input & Output Devices are connected externally 8085 uP D C A Serial Port I / O Ports ROM Input Output TxD RxD RAM
- 3. 12/9/2024 3 Inside Microcontroller Microcontroller – all components of computer system in one integrated circuit (chip)
- 4. 12/9/2024 4 Microprocessor Vs Microcontroller • CPU is stand-alone, RAM, ROM, I/O, timer are separate • General-purpose • Used as CPU in Computer • Instruction sets focus on processing-intensive operations • High processing power • High power consumption • Expensive • CPU, RAM, ROM, I/O ports and timer are all on a single chip • Single-purpose (control- oriented) • Used for applications in which cost, power and space are critical • Bit-level operations • Instruction sets focus on control and bit-level operations • Low power consumption
- 5. 12/9/2024 5 Interfaces with Microcontroller 89C51 3 2 1 6 5 4 9 8 7 # 0 Relay Sensor Stepper Motor
- 6. 12/9/2024 6 Where are microcontrollers used? Microcontroller are used typically where processing power is not critical. • In household appliances like TV,DVD player, audio system, washing machine,microwave etc. • Micro controller applications are in office automation industry • In consumer electronics goods • Used in communication and automobile market • Wherever you need automation • In hand held battery operated devices
- 7. 12/9/2024 7 Advantages of using Microcontrollers • Fast and effective – The architecture correlates closely with the problem being solved (control systems). • Low cost / Low Power – High level of system integration within one component only a handful of components needed to create a working system. • Compatibility – Opcodes and binaries are the SAME for all 80x51 variants. • Multi-sourced – Over 12 manufacturers, hundreds of varieties. • Constant improvement – Improvements in silicon/design increase speed and power annually. • Good documentation • Freely available development tools
- 8. 12/9/2024 8 8051 Microcontroller • The 8051 is 8 bit microcontroller originally developed by Intel in 1980. • It is 40 pin IC. • The 8051 contains. – CPU with Boolean processor. – 5 interrupts (2 external & 3 internal). – 2, 16 bit timer/counter. – Serial port. – 32 I/O lines ( four 8- bit ports). – 128 x 8 bit internal RAM. – 4K x 8 ROM.
- 9. 12/9/2024 9 8051 Functional Blocks
- 10. 12/9/2024 10 Different Internal Blocks Description • I/O Ports – Four 8 bit I/O ports (P0,P1,P2 & P3), i.e. 32 I/O lines • Timers – Two 16 bit up counters, Timer0 and Timer1 – Can be used as timers or event counters – Can interrupt 8051 internally after timeout • Serial I/O – Serial port with TXD and RXD pins can be used with RS232 bus for communication with PC • Interrupts – Total 5 hardware interrupts – Two external active low / edge triggered interrupts (INT0 & INT1) – Three internal interrupts (From Timers & Serial I/O)
- 11. 12/9/2024 11 8051 Pins and Signals
- 12. 12/9/2024 12 8051 Pin & Signals • It is 40 pin IC • Power Supply Vcc = +5V GND = 0V
- 13. 12/9/2024 13 8051 Pins & Signals Vcc GND XTAL1 P0.0 P0.1 P0.2 P0.3 P0.4 P0.5 XTAL2 P0.6 P0.7 P2.0 RST P2.1 EA P2.2 PSEN P2.3 ALE /PROG P2.4 P2.5 P2.6 P2.7 P3.0 P1.0 P3.1 P1.1 P3.2 P1.2 P3.3 P1.3 P3.4 P1.4 P3.5 P1.5 P3.6 P1.6 P3.7 P1.7 8051 Address / Data Bus (AD0 – AD7) Address Bus (A8 – A15) Port 1 R X D T X D INT0 INT1 T0 T1 WR RD Alternate Function Oscillator CLK input
- 14. 12/9/2024 14 Oscillator Connections • Crystal connected to XTAL1 and XTAL2. • One machine cycle = 12 clock cycles • If Crystal frequency is 12 MHz. • 12 MHz clock results in 1usec machine cycle. • Many instruction require only one machine cycle. i.e. 1 usec One Machine Cycle 18 (XTAL2) 19 (XTAL1) 33pF 33pF 12MHz 8051 State 1 State 2 State 6 State 5 State 4 State 3
- 15. 12/9/2024 15 With Reset Circuit (VCC) 40 9 (RST) (EA) 31 18 (XTAL2) 19 (XTAL1) 20 (GND) 33pF 33pF 8K2 12MHz 10µF 8051 +5V
- 16. 12/9/2024 16 Pin Description Signal Name & Function RST Reset: A high on this pin for two machine cycles while the oscillator is running, resets the device. Execute program from 0000H. ALE/PROG Address Latch Enable/Program Pulse: Output pulse for latching the low byte of the address during an access to external memory. This pin is also the program pulse input (PROG) during EPROM programming. PSEN Program Store Enable: The read strobe to external program memory. ( acts like RD for external EPROM) EA/Vpp External Access Enable/Programming Supply Voltage: If EA is held high, the device executes from internal program memory. If EA is held low, the device executes from external program memory. This pin also receives the 12.75V programming supply voltage (VPP) during EPROM programming.
- 17. 12/9/2024 17 I/O Ports (32 I/O Pins) • All I/O pins are bidirectional, each pin can be used independently as input or output • Port 1, 2 & 3 have internal pull-ups. • Port 0 has open drain outputs, hence it need external pull-ups. • Port 0, 2 & 3 are dual purpose. • Port 1 is dedicated I/O port. Port Primary Function Secondary Function P0.7 – P0.0 I/O Lower Address / Data Bus (AD7 – AD0) P1.7 – P1.0 I/O ---- P2.7 – P2.0 I/O Higher Address Bus (A15 – A8) P3.7 – P3.0 I/O RD, WR, T1, T0, INT1, INT0,TXD & RXD
- 18. 12/9/2024 18 8051 Data Memory Space External RAM 64KB FFFFH 0000H AND 128 bytes RAM (Direct and Indirect Addressing) 7FH 00H Internal RAM SFRs (Direct Addressing only) FFH 80H
- 19. 12/9/2024 19 8051 Program Memory Space AND OR Internal 4KB EA = 1 0FFFH 0000H EA = 0 External 64KB FFFFH 0000H External 60KB FFFFH 1000H
- 20. 12/9/2024 20 P0 ALE P2 PSEN EA DATA ADDR OE LATCH 8051 EPROM Interfacing EPROM with 8051 D7 – D0 A7 – A0 A15 – A8 RD
- 21. 12/9/2024 21 Interfacing RAM with 8051 P0 ALE P2 RD WR EA DATA ADDR OE WE LATCH 8051 with internal ROM RAM Vcc P3 D7 – D0 A7 – A0 A15 – A8
- 22. 12/9/2024 22 Alternate Functions of Port 3 Port Pin Alternate Function P3.0 RxD (Serial Input Port) P3.1 TxD (Serial Output Port) P3.2 INT0 ( External Interrupt 0) P3.3 INT1 ( External Interrupt 1) P3.4 T0 (Timer 0 External Input) P3.5 T1 (Timer 1 External Input) P3.6 WR ( External data memory write) P3.7 RD ( External data memory read)
- 23. 12/9/2024 23 Alternate Functions of Port 3 (Cont..) • RD (P3.7) : External data memory read control signal • WR (P3.6) : External data memory write control signal RD(P3.7) WR(P3.6) 8051 OE WE External RAM
- 24. 12/9/2024 24 Alternate Functions of Port 3 (Cont..) • T0 (P3.4) : Timer 0 External input • T1 (P3.5) : Timer 1 External input T0(P3.4) T1(P3.5) 8051 External CLK
- 25. 12/9/2024 25 Alternate Functions of Port 3 (Cont..) • RXD (P3.0) : Serial Input Port • TXD (P3.1) : Serial Output Port RXD(P3.0) TXD(P3.1) 8051 Input data D0 D1 D2 D3 . . . Output data . . . D3 D2 D1 D0
- 26. 12/9/2024 26 Alternate Functions of Port 3 (Cont..) • INT0 (P3.2) : External Interrupt 0 • INT1 (P3.3) : External Interrupt 1 INT0(P3.2) INT1(P3.3) 8051 Level Triggered Edge Triggered OR
- 27. 12/9/2024 27 Interrupt sources of 8051 • Total five Interrupt Sources • Two external interrupt pins ( either low level or falling edge triggered) – INT0 – INT1 • Three internal ( Two of timer and one serial) – Timer 0 overflow – Timer 1 overflow – Serial ( TI or RI )
- 28. 12/9/2024 28 Interrupt Vector Table Interrupt sources Vector Location Addresses Priority INT0 0003H 1st Timer 0 overflow 000BH 2nd INT1 0013H 3rd Timer 1 overflow 001BH 4th TI or RI 0023H 5th
- 29. YCCE, Nagpur MGI 8051 Microcontroller Dr. P. T. Karule Professor Department of Electronics Engineering Yeshwantrao Chavan College of Engineering, Nagpur (M. S.) Email: ptkarule@gmail.com, 412@ycce.in Website: www.ycce.edu 8051 Microcontroller
- 31. 12/9/2024 31 Port Drivers & Latches
- 32. 12/9/2024 32 ALU • ALU :-. – 8 bit ALU used to perform addition, subtraction, increment, decrement, multiplication & division. – Logical operations like ANDing, Oring, XORing, Inverting, Rotating & 1’s Complement. – Boolean operations like bit Set, Reset, Complement,ANDing & ORing. • TMP1 & TMP2 :-. – Temporary registers with ALU, can not be used by programmer. • Accumulator (A) :–. – 8 bit register used to perform arithmetic & logical operations. It is also used transfer data to/from external memory. • Register B :-. – 8 bit register used for multiplication & division.
- 33. 12/9/2024 33 PSW (Program status Word) P - OV RS0 RS1 F0 AC CY PSW.7 PSW.6 PSW.5 PSW.4 PSW.3 PSW.2 PSW.1 PSW.0 Flag Bit Name CY PSW.7 Carry Flag AC PSW.6 Auxiliary Carry Flag F0 PSW.5 Flag 0 available for general purpose RS1 PSW.4 Register Bank Selector Bit 1 RS0 PSW.3 Register Bank Selector Bit 0 OV PSW.2 Overflow Flag P PSW.0 Parity Flag
- 34. 12/9/2024 34 Register Bank Select Flags The starting 32 locations of 128 bytes RAM are used as register banks. The 32 locations are divided into 4 banks of 8 registers each R0 – R7. RS1 RS0 bits are used to select any one out of 4 register banks. RS1 (PSW.4) RS0 (PSW.3) Register Bank selected 0 0 Bank 0 (00H to 07H) 0 1 Bank 1 (08H to 0FH) 1 0 Bank 2 (10H to 17H) 1 1 Bank 3 (18H to 1FH) On Reset
- 35. 12/9/2024 35 Internal Memory • Internal Program Memory (ROM) – 4K bytes of space on chip to store program • Internal Data Memory (RAM) – 128 Location RAM (128 bytes) • Special Function Registers – 21 Registers are used for different functions Program Memory (4K) 0FFFH 0000H Data Memory (128) SFR (21) FFH 80H 7FH 00H
- 36. 12/9/2024 36 Internal RAM (128 bytes) Register Banks Bit addressable General Purpose 7FH 30H 2FH 20H 1FH 00H 80 locations 16 locations 32 locations
- 37. 12/9/2024 37 Register Banks (32 bytes) Register Banks Bit addressable General Purpose 7FH 30H 2FH 20H 1FH 00H SETB PSW.3 CLR PSW.4 R0 R1 R2 R5 R4 R3 R6 R7 R0 R1 R2 R5 R4 R3 R6 R7 R0 R1 R2 R5 R4 R3 R6 R7 R0 R1 R2 R5 R4 R3 R6 R7 1FH 18H 17H 10H 0FH 08H 07H 00H Bank 0 (default) Bank 1 Bank 2 Bank 3 RS1,RS0=01
- 38. 12/9/2024 38 Bit addressable locations Register Banks Bit addressable General Purpose 7FH 30H 2FH 20H 1FH 00H 2FH 2EH 2DH 2CH 2BH 2AH 29H 28H 27H 26H 25H 24H 23H 22H 21H 20H Bit address (7FH to 00H) Byte address 66 27 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 17 18 20 28 30 37 38 3F 40 47 48 4F 50 58 60 68 70 78 79 7A 7B 7C 7D 7E 7F 11 12 14 15 16 19 1A 1B 1C 1D 1E 1F 13 21 22 23 24 25 26 29 2A 2B 2C 2D 2E 2F 31 32 33 34 35 36 39 3A 3B 3C 3D 3E 41 42 43 44 45 46 49 4A 4B 4C 4D 4E 51 52 53 54 55 56 57 59 5A 5B 5C 5D 5E 5F 61 62 63 64 65 67 69 6A 6B 6C 6D 6E 6F 71 72 73 74 75 76 77 SETB 71H CLR 2EH
- 39. 12/9/2024 39 General purpose locations (80) Register Banks Bit addressable General Purpose 7FH 30H 2FH 20H 1FH 00H 7FH 7EH 7DH 7CH 7BH 7AH 79H 78H 33H 32H 31H 30H
- 40. 12/9/2024 40 Special Function Registers (SFRs) Internal RAM (128) SFR (21) FFH 80H 7FH 00H PCON DPH DPL SP P0 TH1 TH0 TL1 TL0 TMOD TCON P1 SBUF SCON P2 IE P3 IP PSW ACC B F8H F0H E8H E0H D8H D0H C8H C0H B8H B0H A8H A0H 98H 90H 88H 80H FFH F7H EFH E7H DFH D7H CFH C7H BFH B7H AFH A7H 9FH 97H 8FH 87H Bit Addressable SFRs 8 bytes Pink background are control SFR
- 41. 12/9/2024 41 Special Function Registers (SFRs) There are different 8 bit registers for defining the operation of timer, serial data transfer, interrupts etc. These registers are called SFRs. The different 21 SFR are – 1. Accumulator 2. Reg. B 3. PSW 4. P0 (Port 0) 5. P1 (Port 1) 6. P2 (Port 2) 7. P3 (Port 3) 8. DPH & DPL (DPTR) 9. SP (Stack Pointer) 10. TH0 & TL0 (Timer0 reg.) 11. TH1 & TL1 (Timer1 reg.) 12. TMOD (Timer Mode reg.) 13. TCON (Timer Control reg.) 14. SCON (Serial Control reg.) 15. SBUF (Serial Buffer reg.) 16. PCON (Power Control reg.) 17. IE (Interrupt Enable reg.) 18. IP (Interrupt Priority reg.)
- 42. 12/9/2024 42 Stack Pointer (SP) • Stack Pointer SP is 8 bit register. It holds address of top of the stack. Only internal 128 bytes RAM can be used as a stack memory for storing stack of data. In 8051 the data is pushed into stack memory from lower address towards higher address. (Opposite of 8085) At power ON RESET 07H is stored in SP. 7FH 09H 08H 07H 00H 07H SP First data is Pushed here
- 43. 12/9/2024 43 Program Counter (PC) • Program Counter (16 bit) The Internal 4KB EPROM or external EPROM are used to store instruction code of program, hence it is called program memory. To execute any instruction, 8051 will fetch instruction code from program memory and to select program memory location, the 16 bit address is transferred from PC and it is automatically gets incremented by 1 to give address of next instruction. Using branching instruction JMP/CALL, new address can be stored in PC. 0000H PC OPCODE 0000H 0001H 0002H 0FFFH (Instruction Codes) Program Memory (4K) Fetch instruction code & then PC = PC + 1
- 44. 12/9/2024 44 Data Pointer (DPTR) • DPTR DPTR is 16 bit register, which consist of two 8 bit registers DPH and DPL. DPH and DPL can be used to store 8 bit data each. DPTR is used to store 16 bit address of memory. data 0000H 0001H 9000H FFFFH External data memory (64K) 9000H DPTR Data transfer to 8051