ttt es overview
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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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Blocks of microprocessor
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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Blocks of microprocessor
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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