Embedded Systems

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SEMINAR REPORT 2011

CERTIFICATE

This is to certify that the seminar report titled ‘’EMBEDDED SYSTEMS’’ submitted by RAJAT M !A" A#AR$A% and &A$A" 'AT!(R)A is a bonafide *or+ done by her under our super,ision is e-cellent.

INTERNAL EXAMINER: Mr. MOHAN SINGH

SUBMITTED BY: RAJAT MOHAN AGARWAL (08231310 8! "AWAN #ATHURIA (08231310 0!

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AC#NOWLEDGEMENT

)nterdependence is a hi/her ,alue than independence. The satisfaction that accompanies the successful completion of any tas+ *ould be incomplete *ithout the mention of people0 *ho made it possible0 *hose constant /uidance and encoura/ement cro*ned our efforts of success. 1irst and foremost0 *e than+ Almi/hty for all !is blessin/s !e sho*ered on us. ) e-press my deep sense of /ratitude and sincere than+s to Mr.M$%&' ()'*% *ithout *hose contribution ) *ould be not able to complete this report on 2EMBEDDED SYSTEMS3. ) *ould li+e to e-press my heartfelt /ratitude to all Teachers and Staffs of R.D. En/ineerin/ 4olle/e for their +ind co5operation . ) also e-tend my than+s to all my friends for their moral support and encoura/ement. %ast but not the least *e than+ our parents and benefactors *ho inspired us al*ays to do my best.

RAJAT MOHAN AGARWAL "AWAN #ATHURIA

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ABSTRACT

Many embedded systems ha,e substantially different desi/n constraints than des+top computin/ applications. "o sin/le characteri6ation applies to the di,erse spectrum of embedded systems. !o*e,er0 some combination of cost pressure0 lon/ life5cycle0 real5time re7uirements0 reliability re7uirements0 and desi/n culture dysfunction can ma+e it difficult to be successful applyin/ traditional computer desi/n methodolo/ies and tools to embedded applications. Embedded systems in many cases must be optimi6ed for life5cycle and business5dri,en factors rather than for ma-imum computin/ throu/hput. There is currently little tool support for e-pandin/ embedded computer desi/n to the scope of holistic embedded system desi/n. !o*e,er0 +no*in/ the stren/ths and *ea+nesses of current approaches can set e-pectations appropriately0 identify ris+ areas to tool adopters0 and su//est *ays in *hich tool builders can meet industrial needs.

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CONTENTS

)ntroduction 9ariety of embedded systems 4lassification Autonomous systems Realtime embedded systems "et*or+ed embedded systems Mobile /ad/ets !ard*are (MS !ard*are $atchdo/ timers

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(MS hard*are architecture Soft*are RT S Embedded Databases ‘e=B’ 1irm*are Desi/n process De,elopment cycle Specification System synthesis )mplementation synthesis &rototypin/ ;? ;@ ;A ;8 ;8 ;8 ;: =< =; =; =; =;

Applications 4ate/ories Aerospace and defence electronics
EMBEDDED SYSTEMS

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Automoti,e Broadcast B entertainment 4onsumerCinternet appliances Data communications Di/ital ima/in/ )ndustrial measurement and control Medical electronics Ser,er )C Telecommunications Mobile data infrastructures !istory 4harecteristics (ser interface &rocessors in embedded systems Ready made computer boards AS)4 and 1&#A solutions &eripherals
EMBEDDED SYSTEMS

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Synchronous Serial 4ommunication )nterface "et*or+s 1ieldbuses Timers Discrete ) Debu//in/ Tools Debu//in/ Relaibility )mmunity A*are &ro/rammin/ !i/h ,s lo* ,olume Embedded soft*are architectures Simple control loop )nterrupt controlled system 4ooperati,e multitas+in/ Micro+ernels and e-o+ernels Monolithic +ernels
EMBEDDED SYSTEMS

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E-otic custom operatin/ systems Additional soft*are components Embedded De,elopment En,ironment !arsh en,ironment 4ost sensiti,ity )nformation Appliance Set5Top Bo-es &ersonal Access De,ices Thin 4lient Residential #ate*ay 4onclusion References ?; ?; ?= ?? ?? ?? [email protected] [email protected] ?A ?A ?8 ?D

INTRODUCTION

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)f *e loo+ around us0 today *e see numerous appliances *hich *e use daily0 be it our today are po*ered by

refri/erator 0 the micro*a,e o,en0 cars0 &DAs etc. Most appliances

somethin/ beneath the sheath that ma+es them do *hat they do. These are tiny microprocessors0 *hich respond to ,arious +eystro+es or inputs. These tiny microprocessors0 *or+in/ on basic assembly lan/ua/es0 are the heart of the appliances. $e call them embedded systems. f all the semiconductor industries0 the embedded systems mar+et place

is the most conser,ati,e0 and en/ineerin/ decisions here usually lean to*ards established0 lo* ris+ solutions. $elcome to the *orld of embedded systems0 of computers that *ill not loo+ li+e computers and *on’t function li+e any thin/ *e are familiar *ith. As the name si/nifies0 an ‘embedded system’ is built into a noncomputin/ de,ice0 say a car0 T9 or toy. $e can define an embedded system as 2a computin/ de,ice0 built in to a de,ice that is not a computer0 and meant for doin/ specific computin/ tas+s3. )n /eneral en/ineerin/ terms0 embedded systems are used for the control of industrial or physical processes. )n computer science terms0 embedded systems are distributed reacti,e systems. Typically these systems ha,e to react to stimuli from their en,ironment in real time. This can be of hi/h importance in situations *here a lot of si/nal

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processin/ must be carried out on the inputs inorder to compute the outputs. e./.0 multimedia applications. Embedded systems ha,e been around us for about as lon/ as computer themsel,es. These *ere first used in the late ;:A<s to control electro mechanical telephone s*itches. As computer industry has mo,ed to*ards smaller systems o,er the last decade or so0 embedded systems ha,e also mo,ed alon/ *ith this trend. An embedded system is a computer system desi/ned to do one or a fe* dedicated andCor specific functions often *ith real5time computin/ constraints. )t is embedded as part of a complete de,ice often includin/ hard*are and mechanical parts. By contrast0 a /eneral5 purpose computer0 such as a personal computer E&4F0 is desi/ned to be fle-ible and to meet a *ide ran/e of end5user needs. Embedded systems control many de,ices in common use today. Embedded systems are controlled by one or more main processin/ cores that are typically either microcontrollers or di/ital si/nal processors EDS&F. 1or e-ample0 air traffic control systems may usefully be ,ie*ed as embedded0 e,en thou/h they in,ol,e mainframe computers and dedicated re/ional and national net*or+s bet*een airports and radar sites Eeach radar probably includes one or more embedded systems of its o*nF.
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Since the embedded system is dedicated to specific tas+s0 desi/n en/ineers can optimi6e it to reduce the si6e and cost of the product and increase the reliability and performance. Some embedded systems are mass5produced0 benefitin/ from economies of scale. &hysically0 embedded systems ran/e from portable de,ices such as di/ital *atches and M&> players0 to lar/e stationary installations li+e traffic li/hts0 factory controllers0 or the systems controllin/ nuclear po*er plants. 4omple-ity ,aries from lo*0 *ith a sin/le microcontroller chip0 to ,ery hi/h *ith multiple units0 peripherals and net*or+s mounted inside a lar/e chassis or enclosure. )n /eneral0 Gembedded systemG is not a strictly definable term0 as most systems ha,e some element of e-tensibility or pro/rammability. 1or e-ample0 handheld computers share some elements *ith embedded systems such as the operatin/ systems and microprocessors *hich po*er them0 but they allo* different applications to be loaded and peripherals to be connected. Moreo,er0 e,en systems *hich do not e-pose pro/rammability as a primary feature /enerally need to support soft*are updates. n a continuum from G/eneral purposeG to GembeddedG0 lar/e application systems *ill ha,e subcomponents at most points e,en if the system as a *hole is Gdesi/ned to perform one or a fe* dedicated functionsG0 and is thus appropriate to call GembeddedG.
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&4 En/inesH A%)I.;4 Mini5)TI embedded board *ith an -DA AMD #eode %I D<< to/ether *ith 4ompact 1lash0 mini&4) and &4) slots0 ??5pin )DE interface0 audio0 (SB and [email protected] RAM An embedded RouterBoard ;;= *ith (.1%5RSMA pi/tail and [email protected]= mini&4) $i51i card *idely used by *ireless )nternet ser,ice pro,iders E$)S&sF in the 46ech Republic. Embedded systems span all aspects of modern life and there are many e-amples of their use. Telecommunications systems employ numerous embedded systems from telephone s*itches for the net*or+ to mobile phones at the end5user. 4omputer net*or+in/ uses dedicated routers and net*or+ brid/es to route data. 4onsumer electronics include personal di/ital assistants E&DAsF0 mp> players0 mobile phones0 ,ideo/ame consoles0 di/ital cameras0 D9D players0 #&S recei,ers0 and printers. Many household appliances0 such as micro*a,e o,ens0 *ashin/ machines and dish*ashers0 are includin/ embedded systems to pro,ide fle-ibility0 efficiency and features. Ad,anced !9A4 systems use net*or+ed thermostats to more accurately and efficiently control
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temperature that can chan/e by time of day and season. !ome automation uses *ired5 and *ireless5net*or+in/ that can be used to control li/hts0 climate0 security0 audioC,isual0 sur,eillance0 etc.0 all of *hich use embedded de,ices for sensin/ and controllin/. Transportation systems from fli/ht to automobiles increasin/ly use embedded systems. "e* airplanes contain ad,anced a,ionics such as inertial /uidance systems and #&S recei,ers that also ha,e considerable safety re7uirements. 9arious electric motors J brushless D4 motors0 induction motors and D4 motors J are usin/ electricCelectronic motor controllers. Automobiles0 electric ,ehicles0 and hybrid ,ehicles are increasin/ly usin/ embedded systems to ma-imi6e efficiency and reduce pollution. ther automoti,e safety systems include anti5

loc+ bra+in/ system EABSF0 Electronic Stability 4ontrol EES4CES&F0 traction control ET4SF and automatic four5*heel dri,e. Medical e7uipment is continuin/ to ad,ance *ith more embedded systems for ,ital si/ns monitorin/0 electronic stethoscopes for amplifyin/ sounds0 and ,arious medical ima/in/ E&ET0 S&E4T0 4T0 MR)F for non5in,asi,e internal inspections. Embedded systems are especially suited for use in transportation0 fire safety0 safety and security0 medical applications and life critical systems as these systems can be isolated from hac+in/ and thus be more reliable. 1or fire safety0 the systems can be desi/ned to be ha,e
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/reater ability to handle hi/her temperatures and continue to operate. )n dealin/ *ith security0 the embedded systems can be self sufficient and be able to deal *ith cut electrical and communication systems. )n addition to commonly described embedded systems based on small computers0 a ne* class of miniature *ireless de,ices called motes are 7uic+ly /ainin/ popularity as the field of *ireless sensor net*or+in/ rises. $ireless sensor net*or+in/0 $S"0 ma+es use of miniaturi6ation made possible by ad,anced )4 desi/n to couple full *ireless subsystems to sophisticated sensors0 enablin/ people and companies to measure a myriad of thin/s in the physical *orld and act on this information throu/h )T monitorin/ and control systems. These motes are completely self contained0 and *ill typically run off a battery source for many years before the batteries need to be chan/ed or char/ed.

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Embedded systems are di,ided into autonomous0 realtime0 net*or+ed B mobile cate/ories.

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They function in standalone mode. Many embedded systems used for process control in manufacturin/ unitsB automobiles fall under this cate/ory. R,&3-)0, ,01,22,2 (.(-,0(: These are re7uired to carry out specific tas+s in a specified amount of time. These systems are e-tensi,ely used to carryout time critical tas+s in process control.

N,-6$r7,2 ,01,22,2 (.(-,0(: They monitor plant parameters such as temperature0 pressure and humidity and send the data o,er the net*or+ to a centrali6ed system for on line monitorin/.

M$1)3, *&2*,-(: Mobile /ad/ets need to store databases locally in their memory. These /ad/ets imbibe po*erful computin/ B communication capabilities to perform realtime as *ell as nonrealtime tas+s and handle multimedia applications. The embedded system is a combination of computer hard*are0 soft*are0 firm*are and perhaps additional mechanical parts0 desi/ned to perform a specific function. A /ood e-ample is an automatic *ashin/ machine or a micro*a,e o,en. Such a system is in direct contrast to a personal computer0 *hich is not desi/ned to do only a specific tas+. But an
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embedded system is desi/ned to do a specific tas+ *ith in a /i,en timeframe0 repeatedly0 endlessly0 *ith or *ithout human interaction.

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#ood soft*are desi/n in embedded systems stems from a /ood understandin/ of the hard*are behind it. All embedded systems need a microprocessor0 and the +inds of microprocessors used in them are 7uite ,aried. A list of some of the common microprocessors families areK The Lilo/ LD family0 )ntel D<@;CIDA family0 Motorola AD' family and the po*er &4 family. 1or processin/ of information and e-ecution of pro/rams0 embedded system incorporates microprocessor or micro5 controller. )n an embedded system the microprocessor is a part of final product and is not a,ailable for repro/rammin/ to the end user. An embedded system also needs memory for t*o purposes0 to store its pro/ram and to

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store its data. (nli+e normal des+tops in *hich data and pro/rams are stored at the same place0 embedded systems store data and pro/rams in different memories. This is simply because the embedded system does not ha,e a hard dri,e and the pro/ram must be stored in memory e,en *hen the po*er is turned off. This type of memory is called R M. Embedded applications commonly employ a special type of R M that can be pro/rammed or repro/rammed *ith the help of special de,ices.

UMS H&r26&r,:
A common obstacle for de,elopers has been the need to de,elop different sets of hard*are and soft*are for different de,ices. An intelli/ent *ashin/ machine uses a hard*are chip different from that used by an intelli/ent *rist *atch. )n addition0 the soft*are runnin/ on the hard*are chip is different. This often results in increased costs and time ta+en for de,elopment. The (ni,ersal Micro SystemE(MSF from cradle technolo/ies is a solution for this problem. (MS is a /eneral purpose chip built around a simple instruction set. )t can be used to de,elop applications for embedded de,ices because all the functionality re7uired for a specific de,ice can be modeled in the soft*are. Since the maMor functionality pro,ided in

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(MS is throu/h soft*are0 the processor and memory units must be ,ery fast and the input0 output units must be pro/rammable and ,ersatile. (MS uses a lar/e number of hi/h speed0 lo* po*er and small R)S4 based processors on a sin/le chip. Each processin/ element coupled *ith t*o di/ital si/nal processors form a multi stream processorEMS&F0 *hich processes ,oluminous chun+s of data. De,elopin/ on (MS represents a si/nificant infrastructure cost sa,in/s0 dramatic decrease in time to mar+et and an unprecedented opportunity to combine many functions and redefine products in the mar+et.

WATCHDOG TIMERS:
*atchdo/ timer that resets the computer unless the soft*are periodically notifies the *atchdo/ subsystems *ith redundant spares that can be s*itched o,er to soft*are Glimp modesG that pro,ide partial function Desi/nin/ *ith a Trusted 4omputin/ Base ET4BF architectureNAO ensures a hi/hly secure B reliable system en,ironment. An Embedded !yper,isor is able to pro,ide secure encapsulation for any subsystem component0 so that a compromised soft*are component cannot interfere *ith other subsystems0 or pri,ile/ed5le,el system soft*are. This encapsulation +eeps faults from

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propa/atin/ from one subsystem to another0 impro,in/ reliability. This may also allo* a subsystem to be automatically shut do*n and restarted on fault detection.

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PROGI/O P R O G I P R O G I P R O G I PROG I/O EMBEDDED SYSTEMS CLOCKS, DEB G NVMEM DRAM CONTROL S S S S M M M M

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PROGI/O P M M M M R O G S S S I P R O G

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MEMORY

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S$/-6&r,:

Embedded soft*are has /ro*n comple- and per,asi,e enou/h to attract the attention of computer scientists. Embedded soft*are’s main tas+ is to en/a/e the physical *orld interactin/ directly *ith sensors B actuators. The most pressin/ problem is ho* to adapt e-istin/ soft*are techni7ues to meet the challen/es of the physical *orld. Soft*are for embedded systems must handle problems beyond those found in application soft*are for des+tops or mainframe computers. Embedded soft*are often has se,eral thin/s to do at once 5 respond to e-ternal e,ents0 cope *ith unusual conditions *ithout human inter,ention *hile bein/ subMected to deadlines. So embedded soft*are is harder to desi/n. Embedded systems are increasin/ly net*or+ed *hich introduced si/nificant complications such as do*nloadable modules that dynamically reconfi/ure the system. Moreo,er0 consumers demand e,er more elaborate functionality *hich /reatly increases soft*are comple-ity. These systems can no lon/er be desi/ned by a sin/le en/ineer0 fine tunin/ tens of +ilobytes of assembly code. Embedded soft*are desi/n is art as much as it is science. $e must +no* ho* fast our system

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operates and +no* ho* critical it is to meet each deadline. )f deadlines are absolute0 then it is a hard real time system else it is a soft real time system. 1unctionality has steadily shifted from hard*are to soft*are. 4 has become the lan/ua/e of choice for embedded pro/rammers0 because it has the benefit of processor independence. %an/ua/es such as 4PP0 Ja,a are also used. !ome de,ices *ill flourish best if they present a uniform A&) to application pro/rammers0 and an ideal interface is Ja,a. pen Ser,ice

#ate*ay )nitiati,eE S#)F 0 a Ma,a based system that combines ser,ices *ith e,ent on security mechanisms0 is definin/ a set of open standard soft*are application interfaces for buildin/ pen Ser,ice #ate*ays includin/ Residential #ate*ays . Embedded #raphical (ser )nterface’s E#()F are /ro*in/ more elaborate day by day. De,elopers no* ha,e to contend *ith such arcana as a color pallet. )n some applications0 an embedded #() has to compete *ith mechanical controls. )n lu-ury cars0 for e./0 #raphical displays are startin/ to replace mechanical speedo meters and tacho meters.9isuali6ation tools are desi/ned to find bu/s that are hard to find *ith theusual 2 Brea+point and e-plore 2 debu//in/ paradi/m. They *or+ beautifully on 2 !eisenber/ bu/s 2 Q so called because they disappear *hen *e start loo+in/ for them.

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Any source code *ritten in 4 or 4PP or assembly lan/ua/e must be con,erted into an e-ecutable ima/e that can be loaded onto a R M chip. 1or this purpose three distinct steps are in,ol,ed. 4ross compiled or assembled to /enerate obMect files. bMect files must be lin+ed into a relocatable pro/ram. &hysical memory address must be assi/ned to the relocatable pro/ram.

RTOS:
To run any soft*are *e need operatin/ system. Embedded systems do not re7uire a complete operatin/ system0 *hich may ma+e the system bul+y0 but only the basic functionalities of the operatin/ system in a real time en,ironment Q RT S. ff5the5shelf

operatin/ systems for these systems be/an to appear in the late ;:8<’s0 and today se,eral do6en ,iable options are a,ailable.Embedded operatin/ systems are a,ailable in ,ariety of fla,oursK $indo*s "T0 %)"(I0 $indo*s 4E >.<0 &alm S0 R"I0 R MD S0 JBED0 RT +ernel0 Tiny B) S0 Turbo tas+0 "ucleus plusCTas+in/0 Diamond0ThreadI ESTUVF etc. ut of these 0 a fe* maMor players ha,e emer/ed 0 such as 9-*or+s0 &S S0 neculeus0 *indo*s 4E0

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ThreadI and linu-. ‘)nferno’ and ‘4hai’ are the t*o popular en,ironments that are used to de,elop applications.

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Embedded Databases are in soft*are applications and in hard*are de,ices0 both mobile and fi-ed. The purpose of Embedded Database is data stora/e and retrie,al *ith minimum inter,ention and minimum system impact. The rapid increase in the number of Telecomputers0 the e-plosi,e /ro*th of E5commerce and /eneral mi/ration to *ireless technolo/ies ha,e put Embedded Database de,elopment on the )T short list. )n a *orld of mobile computers and smart de,ices 0 si6e matters because memory and stora/e are ,ery limited. A +ey factor is a small memory foot print. Embedded database ,endors and de,elopers tend to focus on smallness of their achie,ements. Sybase’s (ltra %ite0 a ,ersion of SR% *hich is any *here portable database has a foot print of @< +ilobytes.

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The internet /i,es machines a *ay to communicate. 1or embedded internet0 communication channels are seen in technolo/ies such as blue tooth0 4Ebus0 upnp and T4&C)&W lin/uistic mechanisms in notions such as Ma,a RM)W !TT& B S"M&. Embeddin/ internet technolo/ies is also called as ‘e=B’ or embedded to business.

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Many authors use soft*are and firm*are in the same sense. Actually firm*are consists of microcode pro/rams e-ecuted from ,ery hi/h speed control stora/e. 4ommonly used obMect pro/rams placed in R Ms and &R Ms are also some times referred to as firm*are. The problem *ith any approach to the field firm*are updates is that if the up/rade contains a fla*0 the tar/et system may become an e-pensi,e doorstop. Many of the pitfalls are ob,ious and strai/ht for*ard0 but some insidious defects don’t appear until after a product has been deployed. Any *ell desi/ned firm*are up/rade system must be able to reco,er from user errors and other catastrophic e,ents to the fullest e-tent possible. The best *ay to accomplish this is to implement a fundamentally sound firm*are update strate/y that a,oids these problems entirely. A micropro/rammer is a system le,el description of ho* an embedded system behe,es before0 durin/ and after the firm*are update process. This is

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desi/ned to help a,oid many of the problems to do*nloadable firm*are. ‘1le-*are’ is a fle-ible firm*are de,elopment en,ironment.

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EMBEDDED SYSTEMS

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Embedded system desi/n is a 7uantitati,e Mob. The pillars of the system desi/n methodolo/y are the separation bet*een function and architecture0 is an essential step from conception to implementation. )n recent past0 the search and industrial community has paid si/nificant attention to the topic of hard*are5soft*are E!$CS$F codesi/n and has tac+led the problem of coordinatin/ the desi/n of the parts to be implemented as soft*are and the parts to be implemented as hard*are a,oidin/ the !$CS$ inte/ration problem marred the electronics system industry so lon/. )n any lar/e scale embedded systems desi/n methodolo/y0 concurrency must be considered as a first class citi6en at all le,els of abstraction and in both hard*are and soft*are. 1ormal models B transformations in system desi/n are used so that ,erification and synthesis can be applied to ad,anta/e in the desi/n methodolo/y. Simulation tools are used for e-plorin/ the desi/n space for ,alidatin/ the functional and beha,iors of embedded systems. !ard*are can be simulated at different le,els such as electrical circuits0 lo/ic /ates0 RT% e.t.c. usin/ 9!D% description. )n some en,ironments soft*are de,elopment tools can be coupled *ith hard*are simulators0 *hile in others the soft*are is e-ecuted on the simulated hard*are. The later approach is feasible only for small parts of embedded systems. timin/

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DE+EL"OMENT CYCLE

Re7uirement analysis
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Desi/n of an embedded system usin/ )ntel’s D<4;DDEB chip is sho*n in the fi/ure. )norder to reduce comple-ity0 the desi/n process is di,ided in four maMor stepsK specification0 system synthesis0 implementation synthesis and performance e,aluation of the prototype.

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Durin/ this part of the desi/n process0 the informal re7uirements of the analysis are transformed to formal specification usin/ SD%.

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1or performin/ an automatic !$CS$ partitionin/0 the system synthesis step translates the SD% specification to an internal system model s*itch contains problem /raphB architecture /raph. After system synthesis0 the resultin/ system model is translated bac+ to SD%.

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SD% specification is then translated into con,entional implementation lan/ua/es such as 9!D% for hard*are modules and 4 for soft*are parts of the system.

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n a prototypin/ platform0 the implementation of the system under de,elopment is e-ecuted *ith the soft*are parts runnin/ on multiprocessor unit and the hard*are part runnin/ on a 1&#A board +no*n as phoeni-0 prototype hard*are for Embedded "et*or+ )nterconnect Accelerators.

A::3)4&-)$'(:

Embedded systems are findin/ their *ay into robotic toys and electronic pets0 intelli/ent cars and remote controllable home appliances. All the maMor toy ma+ers across the *orld ha,e been comin/ out *ith ad,anced interacti,e toys that can become our friends for life. ‘1urby’ and ‘A)B ’ are /ood e-amples at this +ind. 1urbies ha,e a distinct life cycle Must li+e human bein/s0 startin/ from bein/ a baby and /ro*in/ to an adult one. )n A)B first t*o letters

stands for Artificial )ntelli/ence. "e-t t*o letters represents robot . The A)B is robotic do/. Embedded systems in cars also +no*n as Telematic Systems are used to pro,ide na,i/ational security communication B entertinment ser,ices usin/ #&S0 satellite. !ome appliances are
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/oin/ the embedded *ay. %# electronics di/ital D) S refri/erator can be used for surfin/ the net0 chec+in/ e5mail0 ma+in/ ,ideo phone calls and *atchin/ T9.)BM is de,elopin/ an air conditioner that *e can control o,er the net. Embedded systems co,er such a broad ran/e of products that /enerali6ation is difficult. !ere are some broad cate/ories.

CATEGORIES

A,r$(:&4, &'2 2,/,'4, ,3,4-r$')4(:
fire control0 radar0 roboticsCsensors0 sonar.

A5-$0$-);,:
autobody electronics0 auto po*er train0 auto safety0 car information systems.

Br$&24&(- < ,'-,r-&)'0,'-:
Analo/ and di/ital sound products0 camaras0 D9Ds0 Set top bo-es0 ,irtual reality systems0 /raphic products.

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C$'(50,r=)'-,r',- &::3)&'4,(:
Business handheld computers0 business net*or+ computersCterminals0 electronic boo+s0 internet smart handheld de,ices0 &DAs.

D&-& 4$005')4&-)$'(:
Analo/ modems0 ATM s*itches0 cable modems0 IDS% modems0 Ethernet s*itches0 concentrators.

D)*)-&3 )0&*)'*:
4opiers0 di/ital still cameras0 1a- machines0 printers0 scanners.

I'25(-r)&3 0,&(5r,0,'- &'2 4$'-r$3:
!ydro electric utility research B mana/ement traffic mana/ement systems0 train marine ,essel mana/ement systems.

M,2)4&3 ,3,4-r$')4(:
Dia/nostic de,ices0 real time medical ima/in/ systems0 sur/ical de,ices0 critical care systems.

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S,r;,r I=O:
Embedded ser,ers0 enterprise &4 ser,ers0 &4) %A"C")4 controllers0 RA)D de,ices0 S4S) de,ices.

T,3,4$005')4&-)$'( :
ATM communication products0 base stations0 net*or+in/ s*itches0

S "ETCSD! cross connect0 multiple-er.

M$1)3, 2&-& )'/r&(-r54-5r,(:
Mobile data terminals0 pa/ers0 9SATs0 $ireless %A"s0 $ireless phones.

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H)(-$r.

ne of the first reco/ni6ably modern embedded systems *as the Apollo #uidance 4omputer0 de,eloped by 4harles Star+ Draper at the M)T )nstrumentation %aboratory. At the proMectHs inception0 the Apollo /uidance computer *as considered the ris+iest item in the Apollo proMect as it employed the then ne*ly de,eloped monolithic inte/rated circuits to reduce the si6e and *ei/ht. An early mass5produced embedded system *as the Autonetics D5;8 /uidance computer for the Minuteman missile0 released in ;:A;. )t *as built from transistor lo/ic and had a hard dis+ for main memory. $hen the Minuteman )) *ent into production in ;:AA0 the D5;8 *as replaced *ith a ne* computer that *as the first hi/h5,olume use of inte/rated circuits. This pro/ram alone reduced prices on 7uad nand /ate )4s from T;<<<Ceach to T>Ceach0 permittin/ their use in commercial products. Since these early applications in the ;:A<s0 embedded systems ha,e come do*n in price and there has been a dramatic rise in processin/ po*er and functionality. The first microprocessor
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for e-ample0 the )ntel ?<<?0 *as desi/ned for calculators and other small systems but still re7uired many e-ternal memory and support chips. )n ;:8D "ational En/ineerin/ Manufacturers Association released a GstandardG for pro/rammable microcontrollers0 includin/ almost any computer5based controllers0 such as sin/le board computers0 numerical0 and e,ent5based controllers. As the cost of microprocessors and microcontrollers fell it became feasible to replace e-pensi,e +nob5based analo/ components such as potentiometers and ,ariable capacitors *ith upCdo*n buttons or +nobs read out by a microprocessor e,en in some consumer products. By the mid5;:D<s0 most of the common pre,iously e-ternal system components had been inte/rated into the same chip as the processor and this modern form of the microcontroller allo*ed an e,en more *idespread use0 *hich by the end of the decade *ere the norm rather than the e-ception for almost all electronics de,ices. The inte/ration of microcontrollers has further increased the applications for *hich embedded systems are used into areas *here traditionally a computer *ould not ha,e been considered. A /eneral purpose and comparati,ely lo*5cost microcontroller may often be pro/rammed to fulfill the same role as a lar/e number of separate components. Althou/h in this conte-t an embedded system is usually more comple- than a traditional solution0 most of
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the comple-ity is contained *ithin the microcontroller itself. 9ery fe* additional components may be needed and most of the desi/n effort is in the soft*are. The intan/ible nature of soft*are ma+es it much easier to prototype and test ne* re,isions compared *ith the desi/n and construction of a ne* circuit not usin/ an embedded processor.

CHARACTERISTICS

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#umsti- ,ero 4 M0 a tiny0 MA&5based embedded computer5on5module *ith $ifi and Bluetooth.

;. Embedded systems are desi/ned to do some specific tas+0 rather than be a /eneral5purpose computer for multiple tas+s. Some also ha,e real5time performance constraints that must be met0 for reasons such as safety and usabilityW others may ha,e lo* or no performance re7uirements0 allo*in/ the system hard*are to be simplified to reduce costs. =. Embedded systems are not al*ays standalone de,ices. Many embedded systems consist of small0 computeri6ed parts *ithin a lar/er de,ice that ser,es a more /eneral purpose. 1or e-ample0 the #ibson Robot #uitar features an embedded system for tunin/ the strin/s0 but the o,erall purpose of the Robot #uitar is0 of course0 to play [email protected] Similarly0 an embedded system in an automobile pro,ides a specific function as a subsystem of the car itself.

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e5con Systems eS M=8< B eS M><< 4omputer on Modules

>. The pro/ram instructions *ritten for embedded systems are referred to as firm*are0 and are stored in read5only memory or 1lash memory chips. They run *ith limited computer hard*are resourcesK little memory0 small or non5e-istent +eyboard andCor screen.

U(,r )'-,r/&4,

Embedded system te-t user interface usin/ Micro9#A

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Embedded systems ran/e from no user interface at all J dedicated only to one tas+ J to comple- /raphical user interfaces that resemble modern computer des+top operatin/ systems. Simple embedded de,ices use buttons0 %EDs0 /raphic or character %4Ds Efor e-ample popular !D??8D< %4DF *ith a simple menu system. More sophisticated de,ices use /raphical screen *ith touch sensin/ or screen5ed/e buttons pro,ide fle-ibility *hile minimi6in/ space usedK the meanin/ of the buttons can chan/e *ith the screen0 and selection in,ol,es the natural beha,ior of pointin/ at *hatHs desired. !andheld systems often ha,e a screen *ith a GMoystic+ buttonG for a pointin/ de,ice. Some systems pro,ide user interface remotely *ith the help of a serial Ee./. RS5=>=0 (SB0 )X40 etc.F or net*or+ Ee./. EthernetF connection. )n spite of the potentially necessary proprietary client soft*are andCor specialist cables that are needed0 this approach usually /i,es a lot of ad,anta/esK e-tends the capabilities of embedded system0 a,oids the cost of a display0 simplifies BS&0 allo*s to build rich user interface on the &4. A /ood e-ample of this is the combination of an embedded *eb ser,er runnin/ on an embedded de,ice Esuch as an )& cameraF or a net*or+ routers. The user interface is displayed in a *eb bro*ser on a &4 connected to the de,ice0 therefore needin/ no bespo+e soft*are to be installed.

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"r$4,(($r( )' ,01,22,2 (.(-,0(
Secondly0 Embedded processors can be bro+en into t*o broad cate/oriesK ordinary microprocessors EY&F and microcontrollers EY4F0 *hich ha,e many more peripherals on chip0 reducin/ cost and si6e. 4ontrastin/ to the personal computer and ser,er mar+ets0 a fairly lar/e number of basic 4&( architectures are usedW there are 9on "eumann as *ell as ,arious de/rees of !ar,ard architectures0 R)S4 as *ell as non5R)S4 and 9%)$W *ord len/ths ,ary from ?5bit to A?5bits and beyond Emainly in DS& processorsF althou/h the most typical remain DC;A5bit. Most architectures come in a lar/e number of different ,ariants and shapes0 many of *hich are also manufactured by se,eral different companies. A lon/ but still not e-hausti,e list of common architectures areK [email protected];A0 [email protected]<=0 AD!4<D0 AD!4;;0 AD+0 8D'<RC8D'<0 D<@;0 ARM0 A9R0 A9R>=0 Blac+fin0 4;A80 4oldfire0 4 &D0 4ortus A&S>0 eLD0 eLD<0 1R590 !D0 !T?D0 M;A40 M>=40 M)&S0 MS&?><0 &)40 &o*er&40 RD40 R%8D0 S!AR40 S&AR40 STA0 Super!0 T%4S5?80 T%4S5D8<0 T%4S5:<<0 Tri4ore0 [email protected]<0 -DA0 IED<<<0 LD<0 AsA& etc.

R,&2. 0&2, 4$0:5-,r 1$&r2(

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&4C;<? and &4C;<?P are e-amples of standards for ready made computer boards intended for small0 lo*5,olume embedded and ru//edi6ed systems0 mostly -DA5based. These are often physically small compared to a standard &40 althou/h still 7uite lar/e compared to most simple EDC;A5bitF embedded systems. They often use MSD S0 %inu-0 "etBSD0 or an embedded real5time operatin/ system such as Micro4C S5))0 R"I or 9-$or+s. Sometimes these boards use non5-DA processors. )n certain applications0 *here small si6e or po*er efficiency are not primary concerns0 the components used may be compatible *ith those used in /eneral purpose -DA personal computers. Boards such as the 9)A E&)A ran/e help to brid/e the /ap by bein/ &45 compatible but hi/hly inte/rated0 physically smaller or ha,e other attributes ma+in/ them attracti,e to embedded en/ineers. The ad,anta/e of this approach is that lo*5cost commodity components may be used alon/ *ith the same soft*are de,elopment tools used for /eneral soft*are de,elopment. Systems built in this *ay are still re/arded as embedded since they are inte/rated into lar/er de,ices and fulfill a sin/le role. E-amples of de,ices that may adopt this approach are ATMs and arcade machines0 *hich contain code specific to the application. !o*e,er0 most ready5made embedded systems boards are not &45centered and do not use the )SA or &4) busses. $hen a System5on5a5chip processor is in,ol,ed0 there may be little
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benefit to ha,in/ a standari6ed bus connectin/ discrete components0 and the en,ironment for both hard*are and soft*are tools may be ,ery different. ne common desi/n style uses a small system module0 perhaps the si6e of a business card0 holdin/ hi/h density B#A chips such as an ARM5based System5on5a5chip processor and peripherals0 e-ternal flash memory for stora/e0 and DRAM for runtime memory. The module ,endor *ill usually pro,ide boot soft*are and ma+e sure there is a selection of operatin/ systems0 usually includin/ %inu- and some real time choices. These modules can be manufactured in hi/h ,olume0 by or/ani6ations familiar *ith their speciali6ed testin/ issues0 and combined *ith much lo*er ,olume custom mainboards *ith application5specific e-ternal peripherals. #umsti- product lines are a %inu-5centric e-ample of this model.

ASIC &'2 F"GA ($35-)$'(
A common array of n confi/uration for ,ery5hi/h5,olume embedded systems is the system on a chip ESo4F *hich contains a complete system consistin/ of multiple processors0 multipliers0 caches and interfaces on a sin/le chip. So4s can be implemented as an application5specific inte/rated circuit EAS)4F or usin/ a field5pro/rammable /ate array E1&#AF.

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",r):%,r&3(
Embedded Systems tal+ *ith the outside *orld ,ia peripherals0 such asK Serial 4ommunication )nterfaces ES4)FK RS5=>=0 RS5?==0 [email protected] etc.

S.'4%r$'$5( S,r)&3 C$005')4&-)$' I'-,r/&4,:
)=40 S&)0 SS4 and ESS) EEnhanced Synchronous Serial )nterfaceF (ni,ersal Serial Bus E(SBF Multi Media 4ards ESD 4ards0 4ompact 1lash etc.F

N,-6$r7(:
Ethernet0 %on$or+s0 etc.

F),3215(,(:
4A"5Bus0 %)"5Bus0 &R 1)B(S0 etc.

T)0,r(:
&%%EsF0 4aptureC4ompare and Time &rocessin/ (nits

D)(4r,-, IO:
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a+a #eneral &urpose )nputC utput E#&) F Analo/ to Di/italCDi/ital to Analo/ EAD4CDA4F

D,15**)'*:
JTA#0 )S&0 )4S&0 BDM &ort0 B)T&0 and D&: ports

T$$3(
As *ith other soft*are0 embedded system desi/ners use compilers0 assemblers0 and debu//ers to de,elop embedded system soft*are. !o*e,er0 they may also use some more specific toolsK (tilities to add a chec+sum or 4R4 to a pro/ram0 so the embedded system can chec+ if the pro/ram is ,alid. 1or systems usin/ di/ital si/nal processin/0 de,elopers may use a math *or+bench such as Scilab C Scicos0 MAT%AB C Simulin+0 E)4AS%AB0 Math4ad0 Mathematica0or 1lo*Stone DS& to simulate the mathematics. They mi/ht also use libraries for both the host and tar/et *hich eliminates de,elopin/ DS& routines as done in DS&nano RT S and (nison peratin/ System.

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4ustom compilers and lin+ers may be used to impro,e optimisation for the particular hard*are. An embedded system may ha,e its o*n special lan/ua/e or desi/n tool0 or add enhancements to an e-istin/ lan/ua/e such as 1orth or Basic. Another alternati,e is to add a real5time operatin/ system or embedded operatin/ system0 *hich may ha,e DS& capabilities li+e DS&nano RT S. Sometimes0 de,elopment tools for a personal computer can be used if the embedded processor is a close relati,e to a common &4 processor. As the comple-ity of embedded systems /ro*s0 hi/her le,el tools and operatin/ systems are mi/ratin/ into machinery *here it ma+es sense. 1or e-ample0 cellphones0 personal di/ital assistants and other consumer computers often need si/nificant soft*are that is purchased or pro,ided by a person other than the manufacturer of the electronics. )n these systems0 an open pro/rammin/ en,ironment such as %inu-0 "etBSD0 S#i or Embedded Ja,a is re7uired so

that the third5party soft*are pro,ider can sell to a lar/e mar+et.

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DEBUGGING

Embedded debu//in/ may be performed at different le,els0 dependin/ on the facilities a,ailable. 1rom simplest to most sophisticated they can be rou/hly /rouped into the follo*in/ areasK )nteracti,e resident debu//in/0 usin/ the simple shell pro,ided by the embedded operatin/ system Ee./. 1orth and BasicF

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E-ternal debu//in/ usin/ lo//in/ or serial port output to trace operation usin/ either a monitor in flash or usin/ a debu/ ser,er li+e the Remedy Debu//er *hich e,en *or+s for hetero/eneous multicore systems. An in5circuit debu//er E)4DF0 a hard*are de,ice that connects to the microprocessor ,ia a JTA# or "e-us interface. This allo*s the operation of the microprocessor to be controlled e-ternally0 but is typically restricted to specific debu//in/ capabilities in the processor. An in5circuit emulator E)4EF replaces the microprocessor *ith a simulated e7ui,alent0 pro,idin/ full control o,er all aspects of the microprocessor. A complete emulator pro,ides a simulation of all aspects of the hard*are0 allo*in/ all of it to be controlled and modified0 and allo*in/ debu//in/ on a normal &4. (nless restricted to e-ternal debu//in/0 the pro/rammer can typically load and run soft*are throu/h the tools0 ,ie* the code runnin/ in the processor0 and start or stop its operation. The ,ie* of the code may be as !%% source5code0 assembly code or mi-ture of both. Because an embedded system is often composed of a *ide ,ariety of elements0 the debu//in/ strate/y may ,ary. 1or instance0 debu//in/ a soft*are5 Eand microprocessor5F centric embedded system is different from debu//in/ an embedded system *here most of the processin/ is performed by peripherals EDS&0 1&#A0 co5processorF. An increasin/ number of
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embedded systems today use more than one sin/le processor core. A common problem *ith multi5core de,elopment is the proper synchroni6ation of soft*are e-ecution. )n such a case0 the embedded system desi/n may *ish to chec+ the data traffic on the busses bet*een the processor cores0 *hich re7uires ,ery lo*5le,el debu//in/0 at si/nalCbus le,el0 *ith a lo/ic analy6er0 for instance. Tracin/ Real5time operatin/ systems ERT SF often supports tracin/ of operatin/ system e,ents. A /raphical ,ie* is presented by a host &4 tool0 based on a recordin/ of the system beha,ior. The trace recordin/ can be performed in soft*are0 by the RT S0 or by special tracin/ hard*are. RT S tracin/ allo*s de,elopers to understand timin/ and performance issues of the soft*are system and /i,es a /ood understandin/ of the hi/h5le,el system beha,ior. A /ood e-ample is RTI4,ie*0 for RTI4 Ruadros by Ruadros Systems0 )nc..

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RELIABILITY

Embedded systems often reside in machines that are e-pected to run continuously for years *ithout errors0 and in some cases reco,er by themsel,es if an error occurs. Therefore the soft*are is usually de,eloped and tested more carefully than that for personal computers0 and unreliable mechanical mo,in/ parts such as dis+ dri,es0 s*itches or buttons are a,oided. Specific reliability issues may includeK The system cannot safely be shut do*n for repair0 or it is too inaccessible to repair. E-amples include space systems0 undersea cables0 na,i/ational beacons0 bore5hole systems0 and automobiles. The system must be +ept runnin/ for safety reasons. G%imp modesG are less tolerable. ften

bac+ups are selected by an operator. E-amples include aircraft na,i/ation0 reactor control systems0 safety5critical chemical factory controls0 train si/nals0 en/ines on sin/le5en/ine aircraft.

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The system *ill lose lar/e amounts of money *hen shut do*nK Telephone s*itches0 factory controls0 brid/e and ele,ator controls0 funds transfer and mar+et ma+in/0 automated sales and ser,ice. A ,ariety of techni7ues are used0 sometimes in combination0 to reco,er from errorsJboth soft*are bu/s such as memory lea+s0 and also soft errors in the

I005')-. A6&r, "r$*r&00)'*

H)*% ;( 3$6 ;$350,
1or hi/h ,olume systems such as portable music players or mobile phones0 minimi6in/ cost is usually the primary desi/n consideration. En/ineers typically select hard*are that is Must 2/ood enou/h3 to implement the necessary functions.

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1or lo*5,olume or prototype embedded systems0 /eneral purpose computers may be adapted by limitin/ the pro/rams or by replacin/ the operatin/ system *ith a real5time operatin/ system.

E01,22,2 ($/-6&r, &r4%)-,4-5r,(
There are se,eral different types of soft*are architecture in common use.

S)0:3, 4$'-r$3 3$$:
)n this desi/n0 the soft*are simply has a loop. The loop calls subroutines0 each of *hich mana/es a part of the hard*are or soft*are.

I'-,rr5:- 4$'-r$33,2 (.(-,0
Some embedded systems are predominantly interrupt controlled. This means that tas+s performed by the system are tri//ered by different +inds of e,ents. An interrupt could be /enerated for e-ample by a timer in a predefined fre7uency0 or by a serial port controller recei,in/ a byte. These +inds of systems are used if e,ent handlers need lo* latency and the e,ent handlers are short and simple.
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(sually these +inds of systems run a simple tas+ in a main loop also0 but this tas+ is not ,ery sensiti,e to une-pected delays. Sometimes the interrupt handler *ill add lon/er tas+s to a 7ueue structure. %ater0 after the interrupt handler has finished0 these tas+s are e-ecuted by the main loop. This method brin/s the system close to a multitas+in/ +ernel *ith discrete processes.

C$$:,r&-);, 053-)-&(7)'*
A nonpreempti,e multitas+in/ system is ,ery similar to the simple control loop scheme0 e-cept that the loop is hidden in an A&). The pro/rammer defines a series of tas+s0 and each tas+ /ets its o*n en,ironment to 2run3 in. $hen a tas+ is idle0 it calls an idle routine0 usually called 2pause30 2*ait30 2yield30 2nop3 Estands for no operationF0 etc. The ad,anta/es and disad,anta/es are ,ery similar to the control loop0 e-cept that addin/ ne* soft*are is easier0 by simply *ritin/ a ne* tas+0 or addin/ to the 7ueue5interpreter. &reempti,e multitas+in/ or multi5threadin/ )n this type of system0 a lo*5le,el piece of code s*itches bet*een tas+s or threads based on a timer Econnected to an interruptF. This is the le,el at *hich the system is /enerally considered to ha,e an Goperatin/ systemG +ernel. Dependin/ on ho* much functionality is re7uired0 it

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introduces more or less of the comple-ities of mana/in/ multiple tas+s runnin/ conceptually in parallel. As any code can potentially dama/e the data of another tas+ Ee-cept in lar/er systems usin/ an MM(F pro/rams must be carefully desi/ned and tested0 and access to shared data must be controlled by some synchroni6ation strate/y0 such as messa/e 7ueues0 semaphores or a non5 bloc+in/ synchroni6ation scheme. Because of these comple-ities0 it is common for or/ani6ations to use a real5time operatin/ system ERT SF0 allo*in/ the application pro/rammers to concentrate on de,ice functionality rather than operatin/ system ser,ices0 at least for lar/e systemsW smaller systems often cannot afford the o,erhead associated *ith a /eneric real time system0 due to limitations re/ardin/ memory si6e0 performance0 andCor battery life.The choice that a RT S is re7uired brin/s in its o*n issues ho*e,er as the selection must be done prior to startin/ to the application de,elopment process. This timin/ forces de,elopers to choose the embedded operatin/ system for their de,ice based upon current re7uirements and so restricts future options to a lar/e e-tent. The restriction of future options becomes more of an issue as product life decreases. Additionally the le,el of comple-ity is continuously /ro*in/ as de,ices are re7uired to mana/e many ,ariables such as serial0 (SB0 T4&C)&0 Bluetooth0 $ireless %A"0
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trun+ radio0 multiple channels0 data and ,oice0 enhanced /raphics0 multiple states0 multiple threads0 numerous *ait states and so on. These trends are leadin/ to the upta+e of embedded middle*are in addition to a real time operatin/ system.

M)4r$7,r',3( &'2 ,>$7,r',3(
A micro+ernel is a lo/ical step up from a real5time S. The usual arran/ement is that the

operatin/ system +ernel allocates memory and s*itches the 4&( to different threads of e-ecution. (ser mode processes implement maMor functions such as file systems0 net*or+ interfaces0 etc. )n /eneral0 micro+ernels succeed *hen the tas+ s*itchin/ and intertas+ communication is fast0 and fail *hen they are slo*. E-o+ernels communicate efficiently by normal subroutine calls. The hard*are0 and all the soft*are in the system are a,ailable to0 and e-tensible by application pro/rammers.

M$'$3)-%)4 7,r',3(
)n this case0 a relati,ely lar/e +ernel *ith sophisticated capabilities is adapted to suit an embedded en,ironment. This /i,es pro/rammers an en,ironment similar to a des+top

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operatin/ system li+e %inu- or Microsoft $indo*s0 and is therefore ,ery producti,e for de,elopmentW on the do*nside0 it re7uires considerably more hard*are resources0 is often more e-pensi,e0 and because of the comple-ity of these +ernels can be less predictable and reliable. 4ommon e-amples of embedded monolithic +ernels are Embedded %inu- and $indo*s 4E. Despite the increased cost in hard*are0 this type of embedded system is increasin/ in popularity0 especially on the more po*erful embedded de,ices such as $ireless Routers and #&S "a,i/ation Systems. !ere are some of the reasonsK

• &orts to common embedded chip sets are a,ailable. •

They permit re5use of publicly a,ailable code for De,ice Dri,ers0 $eb Ser,ers0 1ire*alls0 and other code.

• De,elopment systems can start out *ith broad feature5sets0 and then the distribution can be confi/ured to e-clude unneeded functionality0 and sa,e the e-pense of the memory that it *ould consume.

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• Many en/ineers belie,e that runnin/ application code in user mode is more reliable0 easier to debu/ and that therefore the de,elopment process is easier and the code more portable. • Many embedded systems lac+ the ti/ht real time re7uirements of a control system. Althou/h a system such as Embedded %inu- may be fast enou/h in order to respond to many other applications.

1eatures re7uirin/ faster response than can be /uaranteed can often be placed in hard*are. Many RT S systems ha,e a per5unit cost. $hen used on a product that is or *ill become a commodity0 that cost is si/nificant.

E>$-)4 45(-$0 $:,r&-)'* (.(-,0(
A small fraction of embedded systems re7uire safe0 timely0 reliable or efficient beha,ior unobtainable *ith the one of the abo,e architectures. )n this case an or/ani6ation builds a system to suit. )n some cases0 the system may be partitioned into a Gmechanism controllerG usin/ special techni7ues0 and a Gdisplay controllerG *ith a con,entional operatin/ system. A communication system passes data bet*een the t*o.
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A22)-)$'&3 ($/-6&r, 4$0:$','-(
)n addition to the core operatin/ system0 many embedded systems ha,e additional upper5 layer soft*are components. These components consist of net*or+in/ protocol stac+s li+e 4A"0 T4&C)&0 1T&0 !TT&0 and !TT&S0 and also included stora/e capabilities li+e 1AT and flash memory mana/ement systems. )f the embedded de,ices has audio and ,ideo capabilities0 then the appropriate dri,ers and codecs *ill be present in the system. )n the case of the monolithic +ernels0 many of these soft*are layers are included. )n the RT S cate/ory0 the a,ailability of the additional soft*are components depends upon the commercial offerin/.

E01,22,2 D,;,3$:0,'- E';)r$'0,'-

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The embedded system may not ha,e a +eyboard0 a screen0 a dis+ dri,e and other peripheral de,ices re7uired for pro/rammin/ and de,elopment tas+s. Therefore most of the pro/rammin/ for embedded systems is done on a host0 *hich is a computer system *ith all the pro/rammin/ tools. nly after the pro/ram has been *ritten0 compiled0 assembled and

lin+ed is it to mo,e to the tar/et or the system that is shipped to the customers. After *ritin/ source file compilin/0 lin+in/0 relocatin/ and portin/ the e-ecutable ima/e into the R M0 you need to test and debu/ the application. nce you ha,e an e-ecutable ima/e

stored as a file on the host computer0 you need a *ay to do*nload that ima/e into a memory de,ice on the tar/et board or de,elopment board and e-ecute it from there. And if you ha,e the ri/ht tools at your disposal0 it *ill be possible to set brea+points in the pro/ram or set brea+ points in the pro/ram or obser,e its e-ecution. These ,arious tools could be a remote debu//er0 simulator0 emulator or an in5circuit emulator. A remote debu//er can be used to do*nload0 e-ecute0 and debu/ embedded soft*are o,er the serial port or net*or+ connection bet*een the host and the tar/et. )n case of embedded systems0 the debu//er e-ecutes on t*o different computer systems Q a remote debu//er consists of t*o pieces of soft*are. The front5end runs on the host computer and pro,ides the human interface0 and the hidden bac+5end runs on the tar/et processor and communicates
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*ith the front5end o,er a communication lin+. The bac+5end pro,ides lo*5le,el control of the tar/et processor and is usually called debu/ monitor. The debu/ monitor resides in the R M and is automatically started *hene,er the tar/et processor is reset. )t monitors the communication lin+ to the host computer and responds to the re7uest from the remote debu//er runnin/ there. Remote debu//ers are the most commonly used tools for do*nloadin/ and testin/ tools durin/ the de,elopment of embedded soft*are Q mainly because of there lo* cost. Remote debu//ers are helpful in monitorin/ and controllin/ the state of embedded soft*are0 but only in in5circuit emulators E)4EsF allo* you to e-amine the state of the processor on *hich that pro/ram is runnin/. )n fact an )4E actually ta+es the place of the processor on your tar/et board0 or in other *ords0 emulates the *or+ of the processor and pro,ides the human interface *ith *hat e-actly is happenin/ on the board in real5time. This also allo*s the )4E to support po*erful debu//in/ features such as hard*are brea+points and real5time tracin/. Many other debu//in/ tools Q such as simulators0 lo/ic analysers and oscilloscopes Q are also a,ailable in embedded systems. A simulator is a completely host5based pro/ram that simulates the functionality and instruction set of the tar/et processor. Althou/h simulators
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ha,e many disad,anta/es0 they are 7uite ,aluable in the early sta/es of the proMect *hen there isn’t as yet any actual hard*are for the pro/rammers to e-periment *ith. The bi//est disad,anta/e of a simulator is that it simulates only the processor. And embedded systems fre7uently contain one or more other peripherals. )nteraction *ith these de,ices can only sometimes be imitated. You may not do much *ith the simulator once you ha,e the actual embedded hard*are a,ailable to you. nce the tar/et hard*are is a,ailable0 you can use lo/ic analysers and oscilloscopes as debu//in/ tools. These are ,ery useful for debu//in/ the interactions bet*een the processor and other chips on the board. These tools only ,ie* si/nals that lie outside the processor0 and cannot control the flo* of e-ecution of your soft*are li+e debu//ers or emulators can. A lo/ic analyser is e7uipment that is desi/ned to find *hether the electrical si/nal it is attached to is currently to lo/ic le,el ; or <. An oscilloscope so another piece of e7uipment for hard*are debu//in/0 and is used to e-amine any electrical si/nal0 analo/ue si/nal0 or di/ital si/nal on the hard*are.

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H&r(% ,';)r$'0,'-

Many embedded systems do not operate in a controlled en,ironment. E-cessi,e heat is often a problem0 especially in applications in,ol,in/ combustion Ee./.0 many transportation applicationsF. Additional problems can be caused for embedded computin/ by a need for protection from ,ibration0 shoc+0 li/htnin/0 po*er supply fluctuations0 *ater0 corrosion0 fire0 and /eneral physical abuse. 1or e-ample0 in the Mission 4ritical e-ample application the computer must function for a /uaranteed0 but brief0 period of time e,en under non5sur,i,able fire conditions.

C$(- (,'()-);)-.
E,en thou/h embedded computers ha,e strin/ent re7uirements0 cost is almost al*ays an issue Ee,en increasin/ly for military systemsF. Althou/h desi/ners of systems lar/e and small may tal+ about the importance of cost *ith e7ual ur/ency0 their sensiti,ity to cost chan/es can ,ary dramatically. A reason for this may be that the effect of computer costs on profitability is more a function of the proportion of cost chan/es compared to the total system cost0 rather than compared to the di/ital electronics cost alone

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I'/$r0&-)$' A::3)&'4,
)n the past0 embedded systems allo*ed information appliances to carry out simple and specific functions only. But *ith the penetration of the )nternet into the homes of many ordinary families0 it *as reali6ed that electric appliances could ma+e human life easier and more con,enient if they could access )nternet information. Electric appliances can no* access the )nternet0 compute and do *hat they *ere not able to do earlier. )n other *ords0 electric appliances are bein/ transformed into information appliances E)AF or *hat may also be called ‘embedded )A’. %i+e the traditional embedded systems0 the embedded information appliance needs only the least amount of hard*are to operate. )t can operate e,en *ithout a hard dis+0 or *ith lo* po*er and small footprint. )A product can be classified into four mainstream productsK5 • Set5Top Bo-es ESTBF

• &ersonal Access De,ice E&ADF

• Thin 4lient ET4F

• Residential #ate*ay Eor !ome #ate*ayF

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Most )A products may be deri,ed0 *ith little or some modifications0 from these four types of products.

S,-?T$: B$>,(
The set5top bo- is dri,in/ the di/ital re,olution ri/ht into your li,in/ room. Your fin/ertips no* command a *ealth of hi/h 7uality di/ital information and di/ital entertainment0 ri/ht from your fa,orite armchair. The set5top bo- re,olutioni6es home entertainment by pro,idin/ ,ibrant tele,ision ima/es *ith crystal clear sound0 alon/ *ith e5mail0 $eb surfin/0 alon/ *ith customi6ed information such as stoc+ 7uotes0 *eather and traffic updates0 on5line shoppin/0 and ,ideo5on5demand0 ri/ht throu/h a traditional tele,ision.

",r($'&3 A44,(( D,;)4,(
&ersonal Access De,ices E&ADsF are *eb terminals that feature con,enient $eb bro*sin/0 email0 and information access capabilities in a li/ht*ei/ht0 mobile form.

T%)' C3),'-

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A thin client is an information access dri,e that pro,ides users *ith remote access to applications and data that are maintained and e-ecuted on a central ser,er. The thin5client computin/ en,ironment consists of an application ser,er0 a net*or+0 and thin5client de,ices. By centrali6in/ deployment and updates of corporate applications0 thin clients allo* for simplified )nformation Systems E)SF mana/ement *ith dramatically increased security.

R,()2,'-)&3 G&-,6&.
The R# mainly pro,ides ,arious +inds of interfaces that lin+ all the electronic de,ices. The R# unli+e the &40 is a ,ery small0 slim and li/ht piece of hard*are and may soon be incorporated inside other popular electronic appliances. )t *ill play the role of an information hub responsible for the e-chan/e of information bet*een all +inds of electronic de,ices in an ordinary home.

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CONCLUSION:

$e are standin/ on the threshold of an e-citin/ ne* a/e of information technolo/y that *ill chan/e our li,es and the future fore,er. Soon *e shall see more and more di/iti6ation of appliances0 and these *ill be fuelled by human need. Embedded systems and )nformation Appliances ha,e ,irtually entered e,ery sphere of our life and they *ill truly chan/e the *ay *e li,e. Embedded systems ha,e ,irtually entered e,ery sphere of our life0 ri/ht from the time *e *or+ out on tread mills to the cars that *e dri,e today. The possibilities in this field are only limited by our ima/ination.Many of the embedded systems are mana/ed by human controllers by some sort of man machine interface5for e-ample a cash re/ister0a cell phone0 a T9 screen or a &4 interface.)t is this MM) that often represents the most costly in,estment in the system’s de,elopment0interms of both time and money.

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REFERENCES

N;O Embedded Systems &ro/rammin/. Miller 1reeman0 San 1rancisco0 )SS" ;<?<5>=8=.

N=O Daniel D. #aMs+i. 1ran+ 9ahid0 SanMi, "arayan B Jie #on/0 Specification and Desi/n of Embedded Systems. &TR &rentice !all0 En/le*ood 4liffs "J0 ;::?.

N>J Jac+ #anssle0 Art of pro/rammin/ Embedded Systems0 Academic &ress0 San Die/o. ;::=.

N?J Shem5To, %e,i B Asho+ A/ra*ala0 1ault Tolerant System Desi/n0 Mc#ra*!ill0 "e* Yor+0 ;::?.

[email protected] "ancy %e,eson0 Safe*areK system safety and computers0 Addison5$esle0;::?..

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NAO $)'')&ED)A

N8O $$$.SEM)"AR&R JE4TS.4 M

NDO $$$.S4R)BD.4 M

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