lecture1-244.ppt

CS244-Introduction to
Embedded Systems and
Ubiquitous Computing
Instructor: Eli Bozorgzadeh
Computer Science Department
UC Irvine
Winter 2010

Winter 2010- CS 244 2
Introduction to Embedded Systems
 Suggested Textbooks:
 Embedded System Design, by F. Vahid and Givargis, Wiley,
2002
 Embedded System Design, by P. Marwedel, Kluwer
Academic, 2003
 Embedded System Design, by Gajski, Abdi, and et. al.,
Springer, 2008
 Other sources
 Lecture notes
 handouts

Winter 2010- CS 244 3
Course outline
 Lectures
 Tue-Thu: 9:30-11:00 a.m.
 DBH 130
 Office hours: email me first to make sure I am available!
 Grading policy:
 25%: homework
 25%: Paper presentation
 Each of you presents a paper assigned to you, assignment: around
week 4 and presentation around week 8-9.
 30%: embedded system Example project (week 6-10)
 20%: Exam (late midterm, week 8-9)

Winter 2010- CS 244 4
Outline
 What are embedded systems?
 Embedded System Components
 Hardware/software
 Embedded System applications
 Model, languages and tools
 Hardware/software co-design and synthesis
 Reconfigurable Computing
 Real time Operating systems
Copyrighted Material adapted from slides by Peter Marwedel, Frank Vahid,
Tony Givargis, Dan Gajski, and Nikil Dutt

Winter 2010- CS 244 5
What’s an Embedded System?
 Embedded systems =
 information processing systems
embedded into a larger product
 Two types of computing
 Desktop – produced millions/year
 Embedded – billions/year
 Non-Embedded Systems
 PCs, servers, and notebooks
 The future of computing!
 Automobiles, entertainment,
communication, aviation, handheld
devices, military and medical
equipments.

Winter 2010- CS 244 6
Embedded Systems
 Devices other than desktop PCs, servers, and
notebooks
 Electricity running through
 Perform something intelligent
 Hardware/software which form a component of a
larger system, but are concealed from user
 Computers camouflaged as non-computers
 The future of computing!
6

Winter 2010- CS 244 7
An Example Embedded System
Digital Camera Block Diagram

Winter 2010- CS 244 8
ES: Simplified Block Diagram
actuators

Winter 2010- CS 244 9
Course Outline
Concept
Specification
HW/SW
Partitioning
Hardware Components
Software Components
Estimation -
Exploration
Hardware
Software
Validation and Evaluation (area, power, performance, …)

Winter 2010- CS 244 10
Components of Embedded Systems
 Analog Components
 Sensors, Actuators, Controllers, …
 Digital Components
 Processor, Coprocessors
 Memories
 Controllers, Buses
 Application Specific Integrated Circuits (ASIC)
 Converters – A2D, D2A, …
 Software
 Application Programs
 Exception Handlers
Hardware
Software

Winter 2010- CS 244 12
Hardware Components of Embedded
Systems- an example
Analog Digital Analog
Memory
Coprocessors
Controllers
Converters
Processor
Interface
Software
(Application Programs)
ASIC

Winter 2010- CS 244 13
Processors
 What is a processor?
 Artifact that computes (runs algorithms)
 Controller and data-path
 General-purpose (GP) processors:
 Variety of computation tasks
 Functional flexibility and low cost at high volumes (maybe)
 Slow and power hungry
 Single-purpose (SP) processors (or ASIC)
 One particular computation task
 Fast and power efficient
 Functional inflexibility and high cost at low volumes (maybe)
13

Winter 2010- CS 244 14
GP/SP Processor Architecture
14
Data-Path
Data
Input
Data
Output
Control
Status
Controller
Control

Winter 2010- CS 244 15
General-purpose processors
 Programmable device used in a
variety of applications
 Also known as “microprocessor”
 Features
 Program memory
 General datapath with large register
file and general ALU
 User benefits
 Low time-to-market and NRE costs
 High flexibility
 Examples
 Pentium, Athlon, PowerPC
IR PC
Register
file
General
ALU
Datapath
Controller
Program
memory
Assembly code
for:
total = 0
for i =1 to …
Control
logic and
State register
Data
memory

Winter 2010- CS 244 16
Application-specific IS processors (ASIPs)
 Programmable processor optimized for a
particular class of applications having
common characteristics
 Compromise between general-purpose
and ASIC (custom hardware)
 Features
 Program memory
 Optimized datapath
 Special functional units
 Benefits
 Some flexibility, good performance, size
and power
 Examples
 DSPs, Video Signal Processors, Network
Processors,..
IR PC
Registers
Custom
ALU
Datapath
Controller
Program
memory
Assembly code
for:
total = 0
for i =1 to …
Control
logic and
State register
Data
memory

Winter 2010- CS 244 17
Application-Specific ICs (ASICs)
 Digital circuit designed to execute
exactly one program
 coprocessor, hardware accelerator
 Features
 Contains only the components needed
to execute a single program
 No program memory
 Benefits
 Fast
 Low power
 Small size
Datapath
Controller
Control
logic
State
register
Data
memory
index
total
+

Winter 2010- CS 244 18
Application Specific Circuits (ASIC)
Custom-designed circuits
necessary if ultimate speed or
energy efficiency is the goal
and large numbers can be sold.
Approach suffers from long
design times and high costs.

Winter 2010- CS 244 19
GP vs. SP Processors
 Programmable controller
 Control logic is stored in
memory
 Fetch/decode overhead
 Highly general data-path
 Typical bit-width (8, 16, 32,
64)
 Complete set of
arithmetic/logic units
 Large set of registers
 High NRE/sale-volume
 Hardwired controller
 No need for program memory
and cache
 No fetch/decode overhead
 Highly tuned data-path
 Custom bit-width
 Custom arithmetic/logic units
 Custom set of registers
 Low NRE/sale-volume
19
GP: ASIC:

Winter 2010- CS 244 20
Storage
 What is a memory?
 Artifact that stores bits
 Storage fabric and access logic
 Write-ability
 Manner and speed a memory can be written
 Storage-permanence
 ability of memory to hold stored bits after they are
written
 Many different types of memories
 Flash, SRAM, DRAM, etc.
 Common to compose memories
20

Winter 2010- CS 244 21
Write-ability
 Ranges of write ability
 High end
 Processor writes to memory simply and quickly
 E.g., RAM
 Middle range
 Processor writes to memory, but slower
 E.g., FLASH, EEPROM
 Lower range
 Special equipment, “programmer”, must be used to write to
memory
 E.g., EPROM, OTP ROM
 Low end
 Bits stored only during fabrication
 E.g., Mask-programmed ROM
21

Winter 2010- CS 244 22
Storage-permanence
 Range of storage permanence
 High end
 Essentially never loses bits
 E.g., mask-programmed ROM
 Middle range
 Holds bits days/months/years after memory’s power source
turned off
 E.g., NVRAM
 Lower range
 Holds bits as long as power supplied to memory
 E.g., SRAM
 Low end
 Begins to lose bits almost immediately after written
 E.g., DRAM
22

Winter 2010- CS 244 23
Memory Types
23
Storage-permanence
Write-ability
Mask-programmed ROM
OTP ROM
EPROM EEPROM Flash
NVRAM
SRAM/DRAM
Ideal
In-system programmable
Nonvolatile

Winter 2010- CS 244 24
Communication
 What is a bus?
 An artifact that transfers bits
 Wires, air, or fiber and interface logic
 Associated with a bus, we have:
 Connectivity scheme
 Serial Communication
 Parallel Communication
 Wireless Communication
 Protocol
 Ports
 Timing Diagrams
 Read and write cycles
 Arbitration scheme, error detection/correction, DMA, etc.
24

Winter 2010- CS 244 25
Serial Communication
 A single wire used for data transfer
 One or more additional wires used for control
(but, some protocols may not use additional
control wires)
 Higher throughput for long distance
communication
 Often across processing node
 Lower cost in terms of wires (cable)
 E.g., USB, Ethernet, RS232, I2C, etc.
25

Winter 2010- CS 244 26
Parallel Communication
 Multiple buses used for data transfer
 One or more additional wires used for control
 Higher throughput for short distance
communication
 Data misalignment problem
 Often used within a processing node
 Higher cost in terms of wires (cable)
 E.g., ISA, AMBA, PCI, etc.
26

Winter 2010- CS 244 27
Wireless Communication
 Infrared (IR)
 Electronic wave frequencies just below visible light spectrum
 Diode emits infrared light to generate signal
 Infrared transistor detects signal, conducts when exposed to
infrared light
 Cheap to build
 Need line of sight, limited range
 Radio frequency (RF)
 Electromagnetic wave frequencies in radio spectrum
 Analog circuitry and antenna needed on both sides of
transmission
 Line of sight not needed, transmitter power determines range
27

Winter 2010- CS 244 28
Peripherals
 Perform specific computation task
 Custom single-purpose processors
 Designed by us for a unique task
 Standard single-purpose processors
 “Off-the-shelf”
 pre-designed for a common task
28

Winter 2010- CS 244 29
Timers
 Timers: measure
time intervals
 To generate timed
output events
 To measure input
events
 Top: max count
reached
 Range and
resolution
29
16-bit up counter
Clk
Cnt
Basic timer
Top
Reset
16

Winter 2010- CS 244 30
Counters
 Counter: like a
timer, but counts
pulses on a general
input signal rather
than clock
 e.g., count cars passing
over a sensor
 Can often configure
device as either a timer or
counter
30
16-bit up
counter
Clk
16
Cnt_in
2x1
mux
Mode
Timer/counter
Top
Reset
Cnt

Winter 2010- CS 244 31
Watchdog Timer
 Must reset timer every X time unit, else timer
generates a signal
 Common use: detect failure, self-reset
31

Winter 2010- CS 244 32
UART
 UART: Universal Asynchronous Receiver
Transmitter
 Takes parallel data and transmits serially
 Receives serial data and converts to parallel
 Parity: extra bit for simple error checking
 Start bit, stop bit
 Baud rate
 Signal changes per second
 Bit rate, sometimes different
32

Winter 2010- CS 244 33
Pulse Width Modulator (PWM)
 Generates pulses with specific high/low
times
 Duty cycle: % time high
 Square wave: 50% duty cycle
 Common use: control average voltage
to electric device
 Simpler than DC-DC converter or digital-
analog converter
 DC motor speed, dimmer lights
33

Winter 2010- CS 244 34
LCD
 Liquid Crystal Display
 N rows by M columns
 Controller build into
the LCD module
 Simple
microprocessor
interface using ports
 Software controlled
34

Winter 2010- CS 244 35
Keypad
35
N1
N2
N3
N4
M1
M2
M3
M4
key_code
keypad controller
k_pressed
key_code
4
N=4, M=4

Winter 2010- CS 244 36
Stepper Motor Controller
 Stepper motor: rotates fixed number of
degrees when given a “step” signal
 In contrast, DC motor just rotates when power
applied, coasts to stop
 Rotation achieved by applying specific
voltage sequence to coils
 Controller greatly simplifies this
36

Winter 2010- CS 244 37
Analog-to-Digital Converter
37
proportionality
Vmax = 7.5V
0V
1111
1110
0000
0010
0100
0110
1000
1010
1100
0001
0011
0101
0111
1001
1011
1101
0.5V
1.0V
1.5V
2.0V
2.5V
3.0V
3.5V
4.0V
4.5V
5.0V
5.5V
6.0V
6.5V
7.0V
Analog to Digital
(A/D)
4
3
2
1
t1 t2 t3 t4
0100 1000 0110 0101
time
analog
input
(V)
Digital output
Digital to Analog
(D/A)
4
3
2
1
0100 1000 0110 0101
t1 t2 t3 t4
time
analog
output
(V)
Digital input

Winter 2010- CS 244 38
Summary
 Hardware: Information Processing
 Processors
 Memories
 Communication
 Peripherals

lecture1-244.ppt

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