computer hardware requirements for real –time applications

8/2/2019 Computer Hardware Requirements for Real Time applications

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Computer HardwareRequirements for Real

Time applications


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Although almost any digital computer can beused for real time computer control and other

real time operations , they are not all equallyeasily adapted for such work.

In the majority of embedded computer-basedsystems the computer used will be a

microprocessor , a microcomputer or aspecialised digital processor.

Specialised digital processors-

Fast digital signal processors

Parallel computers- transputer and specialRISC(reduced instruction set computers)


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General purpose computer

The general purpose microprocessors include

-Intel XX86 series

-Motorola 680XX series

-National 32XXX series

-Zilog Z80 and Z8000 series.


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GENERAL

PURPOSE

REGISTER

ALU CONTROL

MAINMEMORY

INPUT/OUTPUT INTERFACE

PERIPHER

ALS

DATA

CONTROL

ADDRESS

Schematic diagram of a general purposedigital computer


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Central Processing Unit

CPU=ALU+ Control unit + general purposeregister

ALU>carry out arithmetic and logic

operationsGeneral purpose registers>storing data

temporarily while being processed.

Control unit>supervises the operations within

the CPU.--fetches program instructions frommain memory

--decodes the instructions

-- and sets up necessary data pathsand timing cycles for execution of the


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The choice of computer for process controlinclude:

--wordlength;

--instruction set;

--addressing methods;

--no of registers;

--information transfer rate;

--interrupt structure;


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Storage

1.Fast access storage- contains data , pgmand results which are currently beingoperated on.

RAM(random access mem)ROM(read-only mem)

PROM(programmable ROM)

EPROM(electronically PROM)

2.Auxiliary storage-

Disc or magnetic tape.


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Input and Output:

Process I/O;

Operator I/O ;

Computer I/O;

Bus Structure:

Mechanical(physical) structure;

electrical;and

Funtional.


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Bus lines can be divided into threefunctional groups

Address lines;Data lines;

Control and status lines;


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Single-chip microcomputers andmicrocontrollers

All the components necessary for a completecomputer are provided on one single chip.

The microcontroller is similarly a single-chip

device that is specifically intended forembedded computer control applicatios.

The microcomputer is that it typically willhave on board the chip a multiplexed.


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oscilla

tor

ControlProcesing

unitProgramstoreEPROM(4 kbytes)Data storeRAM(128 bytes)

Hardware

timers

Interruptcontroller

Serialcommunicationcontroller

i/oports(4)

External

A typical single chipcomputer


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Specialised processors

Developed for two main purposes:

Safety-critical applications;

Increased computation speed.

for safety-critical applications the approachhas been to simplify the instruction set so called

reduced instruction set computer(RISC). Advantage:

Formal verification(using mathematicalproofs).

It is easier to write assemblers and


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Example- viper(cullyer,1988;dettmer,1986)

Main features are:

Formal mathematical description of processorlogic.

Integer arthmatic(32bits)and no floating pointoperations.

No interrupts- all event handling is done usingpolling

No dynamic memory allocation.


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Parallel computer

Three categories:

SIMD (single instruction stream, multiple datastream.)

MISD (multiple instruction stream, single datastream.)

MIMD (multiple instruction stream, multiple datastream.)


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Controlunit

Processorunit

memory

instructions

data

SISD

computer


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Controlunit1

Controlunit2

Controlunit

n

Processorunit1

Processorunit2

Processorunit

3

Memo

ryunit

instructions

instructions

instructions

Stream1

Stream2

Streamn

MISDcomputer


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Controlunit

Unit1

Unit

n

Unit2

Shared

MemoryOrInter-Connecti

onNetwork

Stream1

Stream2

Streamn

dat

a

data

data

proces

sors

SIMD

computer


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Controlunit1

Controlunit2

Controlunit

n

Unit1

Unit

n

Unit

2

SharedMemoryOrInter-Connection

Network

instructions

instructions

instructions

Stream1

Stream2

Stream

n

data

data

data

processors

MIMD

computer


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MIMD

MIMD systems are obviously the most powerfulclass of parallel computers in that eachprocessor can potentially be executing adifferent pgm on a different data set.

The most widely available MIMD system isINMOS transputer. it has

A CPU.

On-board memory.

External memory interface.

Communication links for direct pt-ptconnection to other transputer chips.


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INMOS developed a special programminglanguage, occam, for use with the transputer.

Occam is based on the assumption that theapplication to be implemented on transputercan be modelled as a set of processes thatcommunicate with each other via channels


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Digital signal processors

Speech processing

Telecommunications

Radar hi-fi systems

computer hardware requirements for real –time applications

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