introdcution to embedded system

8/17/2019 introdcution to embedded system

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Introduction to Embedded

Systems


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Outline

• Embedded systems overview

– What is embedded system – Characteristics

– Elements of embedded system – Trends in embedded system

– Design cycle

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Computing Systems

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• Most of us think of desktop computers

– PC – Laptop

– Mainframe – Server

• Maybe at most handheld computer (PDA)

• Embedded systems: a computing systemthat is part of or is embedded into another

systems.


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What is Embedded Systems?

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• Computing system embedded within

electronic devices• Any device or collection of devices that

contain one of more dedicated computers,

microprocessors, or micro-controllers• Combination of computer hardware and

software designed to perform a specificfunction

• Broad definition: Any computing system

that is not a desktop computer


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Embedded System: Examples

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Embedded System Types

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• General purpose computing

– Personal digital assistant, Video games, set top boxes,

wearable computers, automatic tellers• Control systems

– Fuzzy control, PID control, Vehicle engines, chemical

processes, nuclear power, flight control• Signal processing

– Multimedia data compression

– Digital filtering

• Communication & Networking

– Routers, switches, firewalls, … – Surveillance, wireless sensor, …


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Embedded System Market

• Average household uses about 225

embedded processors; about 35 for theautomobile itself

• Estimated 5 billion embedded processor inuse --- 94% share of world market; IntelPentium, Motorola PowerPC, etc.

combined is only 6%

[source: World Semiconductor Trade Statistics Bluebook]

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Why study embedded systems ?• Key elements of our society today

• Many new applications every day

• Requires knowledge of both software andhardware

– Ignored in traditional computer sciencecurriculum

– Isn’ t it only about hardware? NO !!!

• Experienced embedded systemsdesigners are in high demand and short

supply8


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Embedded systems characteristics:

User ’ s viewpoint• Single function

– Dedicated to a task or tasks• Tight constraints

– Size, power, cost, time-to-market• Real time and reactive

– Respond to environment in real time• Safety critical

– Failure of hw/sw can be life threatening

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Embedded system’ s characteristics:

Developer ’ s viewpoint• Concurrent development of hardware andsoftware: hardware/software codesign

• Variety of microprocessors

• Variety of operating systems mostly real time

(RTOS) – May not even have any OS services like ‘printf ’

• Fewer system resources than desktop system

• Requires specialized development tools

• Debugging extremely difficult

• Hardware and software should be extremelyrobust 10


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Typical Design Constraints• Small Size, Low Weight

– Handheld electronics – Transportation applications weight costs money

• Low Power – Battery power for 8+ hours (laptops often last only 2 hours) – Limited cooling may limit power even if AC power available

• Harsh environment – Heat, vibration, shock – Power fluctuations, RF interference, lightning – Water, corrosion, physical abuse

• Real-time and Safety critical operation – Must function correctly and/or in-time – Must not function incorrectly

• Extreme cost sensitivity – $.05 adds up over 1,000,000 units11


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A typical embedded system

Microprocessor

Address Bus

Data Bus

Status Bus

Glue Logic and

Address Decode

Clock Generation

and Distribution

Real Time Clock

Random Access

Memory - RAM

Read Only

Memory - ROM

( FLASH )

Minimally Requirement for an Embedded System

I/O Interface

( D/A, A/D, Digital )

Communications

Other

PeripheralDevices

To Outside World

To outside worldTo other devices

To host Computer

To User I/F

Watchdog Timer

NMI

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Source: Arnold S. Berger


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Elements of an embedded system

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Microprocessor

• 4, 8, 16, 32, 4 bit bus• CISC, RISC, DSP• Integrated peripherals• Debug/Test Port• Caches

• Pipeline• Multiprocessing Systems

DEBUG PortNon-volatile memory

• EPROM, FLASH, DISK• Hybrid

Volatile Memory

• DRAM, SRAM

• Hybrid

Custom Devices

• ASIC• FPGA• PAL

Standard Devices

• I/O Ports• Peripheral Controllers

Communication Devices

• Ethernet• RS-232• SCSI• Centronics

• Proprietary

Microprocessor Bus

• Custom• PCI• VME

• PC-102

System Clocks• RTC circuitry• System clocks• Integrated in uC• Imported/Exported

Peripheral Bus

Software

• Appl ication Code• Driver Code / BIOS• Real Time Operating System• User Interface• Communications Protoco l Stacks

• C, C++, Assembly Language, ADA• Legacy Code

T o O u t s i d e W o r l d Key Point: Al though vastly d ifferent in complexi ty and design, common

architectural traits allow us to design and debug a wide variety of systems



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Trends in embedded system

• Higher integration

– Microprocessor – Micro-controller

– System-on-Chip (SOC)

• Hardware/software co-design

• Mature design flow

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Higher Integration (1)

• Microprocessor

– An integrated circuitwhich forms thecentral processing unit

for a computer orembedded controller,but requires additionalsupport circuitry to

function

– Example: Pentium, AMD K6 etc.

Progr am

memory

Data

Storage

I/ O

Micr oprocessor I/O

I/ O

Clock To outside

wor ld

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• Micro-controller – A microprocessor plus additional

peripheral support devicesintegrated into a single package

– Peripheral support devices mayinclude:

• Serial ports ( COM ), ParallelPorts, Ethernet ports, A/D & D/A

• Interval timers, watchdog timers,event counter/timers, real time

clock ( RTC )• Other local processors ( DSP,

numeric coprocessor, peripheralcontroller )

– Example: Motorola coldfire

Microprocessor

Core

Program

Memory

Data

Storage

I/O

I/O

Real-time

ClockI/O

To outside world

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• System-on-chip (SOC) – A microprocessor plus additional peripheral

support devices integrated into a single chip – Example: Intel StrongARM

Source: Intel

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Driving Factor

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• Moore’ s Law – Predicted by Intel co-founder Gordon Moore ’ 65

– IC transistor capacity has doubled roughly every18 months for the past several decades

• Process technology can put more and more

functionality on the same chip as CPU at reducedcost

Source: Intel


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Liming Factor • Design productivity gap

– Growing design gap between what technology

can offer and our ability to design in thattechnology

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Source: ITRS’99


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Core based SOC design

• Intellectual Property (IP) circuits or cores arepre-designed and pre-verified functional units

• IP s are reusable implying lower design cost• Core examples:

–Processors: ARM, PowerPC, .. – Memory: RAM, memory controller, …

– Peripherals: PCI, DMA controller, …

– Multimedia: MPEG/JPEG encoder/decoder … – Digital Signal Processor (DSP)

– Telecommunication: Ethernet controller, router, ..

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Hardware/Software Co-design• In the past:

– Hardware and

software designtechnologies werevery different

• At present – Recently matured

synthesis technique

enables a unified viewof hardware andsoftware

Implementation

Assembly instructions

Machine instructions

Register transfers

Compilers

(1960's,1970's)

Assemblers, linkers

(1950's, 1960's)

Behavioral synthesis

(1990's)

RT synthesis

(1980's, 1990's)

Logic synthesis

(1970's, 1980's)

Microprocessor plus

program bits: “software”

VLSI, ASIC, or PLD

implementation: “hardware”

Logic gates

Logic equations / FSM's

Sequential program code (e.g., C, VHDL)

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The choice of hardware versus software for a particular function is simply a tradeoff among various

design metrics, like performance, power, size, cost, and especially flexibility; there is no fundamental

difference between what hardware or software can implement.

Source: Vahid/Givargis


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Design Flow

Requirements

Specification

Architecture

Components

System Integration

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Requirements

• Functional – Inputs and Outputs

• Analog/Digital/Mechanical

• Periodic/Non-periodic/Bits per data

• Button/Display

– Functions• What does the system do?

• Non-functional

– Performance – Manufacturing cost

– Power consumption

– Physical size and weight23


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Specification

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• A precise description of the requirements

• Unambiguous and understandable

• Unified Modeling Language (UML) is avisual language that nicely captures the

specification – Blurs the distinction between h/w and s/w

– UML models the behavior of embedded system – Automatic code generator could generate HDL

or C++ code for the actual design

implementation


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Architecture Design

• How the system implements the functions

described in the specification• System structure in terms of components

• Hardware/Software partitioning – Hardware and software in embedded system

work together to solve a problem

– Partitioning decision is usually dictated byspeed, flexibility, and cost

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Architecture Design (Contd.)

Technology Performance/

Cost

Time until

running

Time to high

performance

Time to change

code functionality

ASIC Very High VeryLong

Very Long Impossible

FPGA Medium Medium Long Medium

ASIP/

DSP

High Long Long Long

Generic Low-Medium

Very

Short

Not Attainable

Very Short

F l e x i b i l i t y

S p e e d

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Component Design & System

Integration

• Implementing hardware and software• Putting components together

• Verification

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What is expected of embedded


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What is expected of embedded

system designer?• Need to understand the big picture

• Hardware can no longer be a black box• Design software with

– Real time constraints – Low power

– Small code size

• Willing to acquire domain specificknowledge

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Techniques needed in


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Techniques needed in

Embedded Systems

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• Low-level: Microcontrollers, FPGA/ASIC,

assembly language, A/D, D/A – Device Drivers

• High-level: Object oriented Design, C/C++,

Real Time Operating Systems – May use Java, Windows CE, Linux, …

• Meta-level: Creative solutions to highlyconstrained problems

• Likely in the future: Unified Modeling

Language, embedded networks


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References

• Embedded Systems Design: An

Introduction to Processes, Tools andTechniques, by Arnold S. Berger, CMPBooks, 2001

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Documents

introdcution to embedded system