TTT ES Overview

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2Tessolve Training Development Institute

Table of ContentsDefinition of embedded systemEmbedded System componentsExamples of embedded system

Classification of embedded systemCharacteristics of an embedded systemComparison: General purpose and Embedded systemBlocks of microprocessorBlocks of microcontrollerVon-Neumann and Harvard architectureRISC and CISC instruction setMemoryPeripheralsChallenges in Embedded System designClassical design methodology

Software development models


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Components of embedded system

Generic components

Processoror ASIC

D/Aconversion Actuators

A/DconversionSensors

Memory

Diagnosticport

Userinterface

Externalenvironment


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Examples of Embedded System


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Examples of Embedded System


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Characteristics of Embedded SystemSpecial-purpose

Typically, is designed toexecute a single program,repeatedlyIt used to be single-purpose

Now, multi-functioned, butsingle-purpose


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Characteristics of Embedded SystemTightly constrained

Low costSimple systemsFewer components basedPerforms functions fastenoughMinimum power


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Characteristics of Embedded System

ReactiveContinually reacts to externalevents

Real-time

Must compute certainresults in real-time


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Characteristics of Embedded System

Hardware and software co-

existThe software written forembedded systems is oftencalled firmware

Is stored in read-only memory orFlash memory chips rather thana disk drive


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Comparison: General purpose and Embeddedsystem

Embedded System

Not programmable byend userDesigned only forspecific applicationLimited memorySuitable for realizingreal-time requirements

Compact

General Purpose System

Programmable by the enduserCan be designed for broadclass of applicationMemory is not a constraintNot suitable for realizingreal-time requirements

Bulky


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Blocks of microprocessor

Microprocessor

ControlUnit

Registers

Registers

InstructionCache

Arithmetic& Logic

Unit

Bus

InterfaceUnit

DataCache

InstructionDecoder

Floating

PointUnit

I/O

RAM

MemoryBus

SystemBus


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Bus interface unitReceives instructions & data from main memoryInstructions are then sent to the instruction cache,data to the data cacheAlso receives the processed data and sends it to themain memory

Instruction DecoderThis unit receives the programming instructions anddecodes them into a form that is understandable bythe processing units, i.e. the ALU or FPUThen, it passes on the decoded instruction to the ALUor FPU


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Blocks of microprocessorArithmetic & Logic Unit (ALU)

Also known as the Integer UnitIt performs whole-number math calculations (subtract,multiply, divide, etc) comparisons (is greater than, issmaller than, etc.) and logical operations (NOT, OR, AND,etc)

Floating-Point Unit (FPU)Also known as the Numeric UnitIt performs calculations that involve numbers representedin floating-point numbers

Floating-point calculations are required for doinggraphics, engineering and scientific workThe ALU can do these calculations as well, but will dothem very slowly


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RegistersBoth ALU & FPU have a private memory placed rightnext to them for their exclusive use. These are calledregistersThe ALU & FPU store intermediate and final results fromtheir calculations in these registers

Processed data goes back to the data cache and then tomain memory from these registers

Control Unit

The brain of the uPManages the whole uP tasks include fetching instructions& data, storing data, managing input/output devices


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RISC and CISC instruction setInstruction Set

The set of machine instructions that a uP recognizesand can execute

Two different approaches:Reduced Instruction Set Computers (RISC)

Instruction set as small and simple as possible.Minimizes amount of circuitry --> faster computers

Complex Instruction Set Computers (CISC)More instructions, many very complexEach instruction can do more work, but require morecircuitry.


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Memory: Write ability and permanence


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Memory: Write ability and permanenceRanges of write ability

High endprocessor writes to memory simply and quicklye.g., RAM

Middle rangeprocessor writes to memory, but slowere.g., FLASH, EEPROM

Lower rangespecial equipment, programmer, must be used to write tomemorye.g., EPROM, OTP ROM

Low endbits stored only during fabricatione.g., Mask-programmed ROM


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Memory: Write ability and permanenceRange of storage permanence

High end

essentially never loses bitse.g., mask-programmed ROMMiddle range

holds bits days, months, or years after memorys power source

turned offe.g., NVRAMLower range

holds bits as long as power supplied to memory

e.g., SRAMLow end

begins to lose bits almost immediately after writtene.g., DRAM


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Memory HierarchyProcessor

Cache

Main memory

Disk

Tape

RegistersAccess timeincreases

costincreases

Large, inexpensive,slow memory stores

entire program anddata

Small, expensive, fast memory storescopy of likely accessed

parts of larger memory


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PeripheralsFlash memoryRAM

Serial portsWDTTimerADCDACSensorsActuators

RTCI/O devices


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Challenges in Embedded System design

Correct functioning is crucialsafety-critical applications

They are Reactive SystemsOnce started run forever.Termination is a bad behavior.

Concurrent systemsSystem and environment run concurrently

Real-time systemsnot only rt. outputs but at rt. timeimagine a delay of few minutes in pacemaker system

Stringent resource constraintscompact systems ,quick response , low power ,Time-to-market


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Software development modelsWaterfall model

Determine basic characteristics of system

Decompose into basic modules

Implement and integrate

Exercise and uncover bugs

Fix bug & upgrade

Critiques of waterfall model


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Software development modelsSpiral Model

Spiral model critiques


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Software development models

V- Model


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TTT ES Overview

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