《IT專業(yè)英語》課件UNIT13

UNIT13EmbeddedSystem

13-1TechnicalPart13-2ReadingMaterial

13-1TechnicalPart

13-1-1Definition

Anembeddedsystemisacomputersystemdesignedforspecificcontrolfunctionswithinalargersystem,oftenwithreal-timecomputingconstraints(SeeFigure13-1).Itisembeddedaspartofacompletedeviceoftenincludinghardwareandmechanicalparts.Bycontrast,ageneral-purposecomputer,suchasapersonalcomputer(PC),isdesignedtobeflexibleandtomeetawiderangeofend-userneeds.Embeddedsystemscontrolmanydevicesincommonusetoday.13-1-2Introductions

ComponentsofanEmbeddedSystem

Anembeddedsystemisonethathascomputer-hardwarewithsoftwareembeddedinitasoneofitsmostimportantcomponent.Itisadedicatedcomputer-basedsystemforanapplication(s)orproduct.Itmaybeeitheranindependentsystemorapartofalargersystem.AsitssoftwareusuallyembedsinROM(ReadOnlyMemory)itdoesnotneedsecondarymemoriesasinacomputer.Anembeddedsystemhasthreemaincomponents:Figure13-1PictureoftheinternalsofanADSLmodem/router.Amodernexampleofanembeddedsystem.Labelledpartsincludeamicroprocessor(4),RAM(6),andflashmemory(7).

1.Ithashardware.Figure13-2showstheunitsinthehardwareofanembeddedsystem.Figure13-2theComponentsofanEmbeddedSystemHardware

2.Ithasmainapplicationsoftware.Theapplicationsoftwaremayperformconcurrentlytheseriesoftasksormultipletasks.

3.IthasaRealTimeOperatingSystem(RTOS)thatsupervisestheapplicationsoftwareandprovidesamechanismtolettheprocessorrunaprocessasperschedulinganddothecontext-switchbetweenthevariousprocesses(tasks).

RTOSdefinesthewaythesystemworks.Itorganizesaccesstoaresourceinsequenceoftheseriesoftasksofthesystem.Itschedulestheirworkingandexecutionbyfollowingaplantocontrolthelatenciesandtomeetthedeadlines.Latencyreferstothewaitingperiodbetweenrunningthecodesofataskandtheinstanceatwhichtheneedforthetaskarises.Itsetstherulesduringtheexecutionoftheapplicationsoftware.Asmall-scaleembeddedsystemmaynotneedanRTOS.

Anembeddedsystemhassoftwaredesignedtokeepinviewthreeconstraints:(i)availablesystemmemory,(ii)availableprocessorspeedand(iii)theneedtolimitpowerdissipationwhenrunningthesystemcontinuouslyincyclesofwaitforevents,run,stopandwake-up.CharacteristicsofEmbeddedSystem

1.Embeddedsystemsaredesignedtodosomespecifictask,ratherthanbeageneral-purposecomputerformultipletasks.Somealsohavereal-timeperformanceconstraintsthatmustbemet,forreasonssuchassafetyandusability,othersmayhavelowornoperformancerequirements,allowingthesystemhardwaretobesimplifiedtoreducecosts.2.Embeddedsystemsarenotalwaysstandalonedevices.Manyembeddedsystemsconsistofsmall,computerizedpartswithinalargerdevicethatservesamoregeneralpurpose.Forexample,theGibsonRobotGuitarfeaturesanembeddedsystemfortuningthestrings,buttheoverallpurposeoftheRobotGuitaris,ofcourse,toplaymusic.Similarly,anembeddedsysteminanautomobileprovidesaspecificfunctionasasubsystemofthecaritself.3.Theprograminstructionswrittenforembeddedsystemsarereferredtoasfirmware,andarestoredinread-onlymemoryorFlashmemorychips.Theyrunwithlimitedcomputerhardwareresources:littlememory,smallornon-existentkeyboardorscreen.ClassificationofEmbeddedSystems

Wecanclassifyembeddedsystemsintothreetypesasfollows:

1.SmallScaleEmbeddedSystems:Thesesystemsaredesignedwithasingle8-or16-bitmicrocontroller,theyhavelittlehardwareandsoftwarecomplexitiesandinvolveboard-leveldesign.Theymayevenbebatteryoperated.Whendevelopingembeddedsoftwareforthese,aneditor,assemblerandcrossassembler,specifictothemicrocontrollerorprocessorused,arethemainprogrammingtools.

Usually,‘C’isusedfordevelopingthesesystems.‘C’programcompilationisdoneintotheassembly,andexecutablecodesarethenappropriatelylocatedinthesystemmemory.Thesoftwarehastofitwithinthememoryavailableandkeepinviewtheneedtolimitpowerdissipationwhensystemisrunningcontinuously.

2.MediumScaleEmbeddedSystems:Thesesystemsareusuallydesignedwithasingleorfew16-or32-bitmicrocontrollersorDSPsorReducedInstructionSetComputers(RISCs).Thesehavebothhardwareandsoftwarecomplexities.Forcomplexsoftwaredesign,therearethefollowingprogrammingtools:RTOS,Sourcecodeengineeringtool,Simulator,DebuggerandIntegratedDevelopmentEnvironment(IDE).

Softwaretoolsalsoprovidethesolutionstothehardwarecomplexities.Anassemblerisoflittleuseasaprogrammingtool.ThesesystemsmayalsoemploythereadilyavailableASSPsandIPsforthevariousfunctions—forexample,forthebusinterfacing,encrypting,deciphering,discretecosinetransformationandinversetransformation,TCP/IPprotocolstackingandnetworkconnectingfunctions.ASSPsandIPsmayalsohavetobeappropriatelyconFiguredbythesystemsoftwarebeforebeingintegratedintothesystem-bus.

3.SophisticatedEmbeddedSystems:Sophisticatedembeddedsystemshaveenormoushardwareandsoftwarecomplexitiesandmayneedscalableprocessorsorconfigureurableprocessorsandprogrammablelogicarrays.Theyareusedforcuttingedgeapplicationsthatneedhardwareandsoftwareco-designandintegrationinthefinalsystem,however,theyareconstrainedbytheprocessingspeedsavailableintheirhardwareunits.

Certainsoftwarefunctionssuchasencryptionanddecipheringalgorithms,discretecosinetransformationandinversetransformationalgorithms,TCP/IPprotocolstackingandnetworkdriverfunctionsareimplementedinthehardwaretoobtainadditionalspeedsbysavingtime.Someofthefunctionsofthehardwareresourcesinthesystemarealsoimplementedbythesoftware.Developmenttoolsforthesesystemsmaynotbereadilyavailableatareasonablecostormaynotbeavailableatall.Insomecases,acompilerorretargetablecompilermighthavetobedevelopedforthese.AretargetablecompilerisonethatconFiguresaccordingtothegiventargetconFigureurationinasystem.EmbeddedOperatingSystem

Anembeddedoperatingsystem(EOS)isasystemsoftwarethatmanagesalltheotherprogramsanddevicesinanembeddedsystem.Itnormallyguaranteesacertaincapabilitywithinaspecifiedstoragesizeandtimeconstraintaswellaswithapplicationprograms.Itsstructureisverysimilartoastructureofanormaloperatingsystemhowevermainlydifferentiatedbysomefactorssuchastypeofpreinstalleddevice,functionallimits,takingdesignedjobonly.

Italsonormallyhasbootloader,OSkernel,requireddevicedrivers,filesystemsfortheuserdataandsoforth.Attheircore,embeddedoperatingsystemscontainsomeofthesamesoftwarecomponentsusedonlargeroperatingsystems,suchaswindowsandLinuxetc.largeroperatingsystems(OS),embeddedoperatingsystemsdealswithtaskswitching,schedulingoftasks,memoryallocation,etc.

ButtherearesomedistinctionsbetweendesktopcomputerOSandembeddedsystemOS.DesktopComputerisageneralpurposecomputingsystemwhereasembeddedsystempurposeisforaspecifictask.Embeddedoperatingsystemshaveseveralcommoncharacteristicsthatdistinguishsuchsystemsfromothercomputingsystems:

SingleFunctioned:Usuallyexecutesaspecificprogramrepeatedlye.g.pager.

TightlyConstrained:Allcomputingsystemshaveconstraintsondesignmetrics,butthoseonembeddedsystemscanbeespeciallytight.Adesignmetricisameasureofanimplementation’sfeatures,suchascost,size,performanceandpower.

ReactiveandRealTime:Manyembeddedsystemsmustcontinuallyreacttochangesinthesystem’senvironmentandmustcomputecertainresultsinrealtimewithoutdelay.Incontrast,adesktopsystemtypicallyfocusesoncomputationwithrelativelyinfrequentreactionstoinputdevices.

SecondaryMemory:Generallyembeddedsystemdoesn’tneedsecondarymemory.

Unlikeadesktopcomputersystemwhichmayhavenewsoftwareloadedontoitfrequently,embeddedsystemsretainthesamecodeforalongtime,sometimesindefinitely.Embeddedoperatingsystemsdonotusuallyincludesupportforexternalstorageorgraphicalinterfaces,orprotectionfrommaliciousorunstablecode.Thelimitedmemoryinembeddedsystemsrequirestheoperatingsystemandprocesstoworkverycloselytomanagethefreeresources.13-1-3ApplicationCaseorExample

WashingMachine

Washingmachinesupportsthreefunctionalmodes:

1.FullyAutomaticMode:Infullyautomaticmode,oncethesystemisstarteditperformindependentlywithoutuserinterferenceandafterthecompletionofworkitshouldnotifytheuseraboutthecompletionofwork.Thismodeinstantaneouslysenseclothqualityandrequirementofwater,watertemperature,detergent,load,washcycletimeandperformoperationaccordingly.

2.SemiAutomaticMode:Inthissemiautomaticmodeinwhichwashingconditionsarepredefined.Oncethepredefinedmodeisstartedthesystemperformitsjobandaftercompletionitinformtheuseraboutthecompletionofwork.

3.ManualMode:Inthismode,userhastospecifywhichoperationhewantstodoandhastoproviderelatedinformationtothecontrolsystem.Forexample,ifuserwantstowashclothesonly,hehastochoose‘wash’optionmanually.Thenthesystemasktheusertoenterthewashtime,amountofwaterandtheload.Afterthesedataareentered,theusershouldstartthemachine.Whenthespecifiedoperationiscompletedsystemshouldinformtheuser.

RememberthatModesshouldbeaselectablebyakeypad.

AwashingmachinemayhaveaSystemController(BrainoftheSystem)whichprovidesthepowercontrolforvariousmonitorsandpumpsandevencontrolsthedisplaythattellsushowthewashcyclesareproceeding.AwashingmachinecomprisesseveralcomponentsasshowninFigure13-3.Figure13-3thecomponentsofwashingmachine

Theworkingofthesecomponentsisasfollows:

1.?DisplayPanel:Itisatouchpanelscreentocontrolalltheoperationsofamachine

2.Sensor:Itmeasuresthewaterlevelandappropriateamountofsoap.Inputdevicesforautomaticwashingmachinearesensorsforwaterflow,waterlevelandtemperature,doorswitch,selectorknoborbuttonsforsettingssuchasspinspeed,temperature,loadsizeandtypesofwashcyclerequired.

WaterLevelSensor:Itindicatesbeepsoundwhenwaterlevelislowinwashingtub.

DoorSensor:Itindicatesbeepsoundwhenallclothesarewashedthatmeansnowyoucanopenthemachingdoorandalsoyoucanmovetoyournextphase.NextphasewillbedryPhase.Thisphasealsofollowssameconceptfordryingtheclothes.

3.DrivingMotor:Motorcanrotateintwodirectionseither“reverse’or‘forward’.Theforwarddirectiondrivesthecurrentinforwarddirectionandmotorrotatesforward.Thereversedirectiondriverdoestheoppositeofit.Awashingmachinecanmaintainsinglemotorinfullyautomaticordoublemotorinsemiautomaticwashingmachine.

Sequenceofwashingtheclotheswiththiscanbeexplainedinfewstepsasfollows:

1)Putonyourdirtyclothesontothewashtubforwashing.

2)PutthedetergentSoap(ofyourchoicelikeSurfnExceletc.).

3)PutONthetap,waterrushesinsidethetub.

4)Ifitselectroniccontrol,thenbythepressofthekeys,youcouldprogram,ifitsmechanicalitshallsomethinglikeanmechanicalswitcheswhereinyouareallowedtooperateforsettingthewashtime.

5)Nowthewashmotorrotatesandwashestheclothesandgivesyouabeepsound

6)Nowyourclothesarewashed…removeitfromthewashtubandputitonthespintubandprogramitaccordingly…afterspinningclothesaredriedandyouareallowedtohangitforproperdryinginsunlight.

Thefullyautomaticalsocomesintwocategoryfrontloadingaswellastoploading.

1)Frontloadingistheonewhereinyouaregivenanopeningtoputclothesinonthefrontside.

2)Toploadingisonthetop.

4.SystemController:SuchComponentisusedtocontrolthemotorspeed.Motorcanmoveinforwarddirectionaswellasreversedirection.SystemControllerreadsthespeedofmotorandcontrolsthespeedofmotorindifferentphasessuchasinwashing,cleaning,dryingetc.AllkindsofSensorssuchasDoorSensor,PressureSensorandKeypad,Speedsensorarealsomaintainedbythis.

5.WaterPump:Thewaterpumpisusedtorecirculatewateranddrainoutthedirtywater.Thispumpactuallycontainstwoseparatepumpsinsideone:Thebottomhalfofthepumpishookeduptothedrainline,whilethetophalfrecirculatesthewashwater.Themotorthatdrivesthepumpcanreversedirection.Itspinsonewaywhenthewasherisrunningawashcycleandrecirculatesthewater,anditspinstheotherwaywhenthewasherisdoingaspincycleanddrainingthewater.

13-2ReadingMaterial

13-2-1Readingcomprehension

TrendofTinyEmbeddedSystems

Significantadvancesinmicroelectronicstechnologymadetheincreasingminiaturizationofembeddedsystemspossible.Thistrendtominiaturizationbeganinthelate1960sand,asstatedbyMoore’sLawthatthepowerofmicroprocessorsdoublesaboutevery18months,hasheldtruewithastonishingaccuracyandconsistencyuntilthebeginningofthe21stcentury.

AnannouncementlikethatbyIBMconcerningtheuseof29.9nmtechnologytoprintcircuitsindicatesthatthistrendwillcontinueforanumberofchipgenerations.

Thetrendisleadingtoandwillresultinthedevelopmentoftinyembeddedsystems,integratedintomoreandmoreeverydayobjects.Andwillcreateaworldofsmartdevicessurroundingus.Forexample,parentswillnolongerlosetrackoftheirchildren,eveninthebusiestcrowds,whenlocationsensorsandcommunicationmodulesaresewnintotheirclothes.Similardevicesattachedtotimetablesandsignpostscouldguideblindorforeignpeopleinunknownenvironmentsbytalkingtothem.

Anotherinterestingpossibilityofferedbysuchtechnologywouldbethecreationofintelligenthomeswherearefrigeratorcandetectoldfood,awashingmachinecanquerytheinstructionsfordirtyclothes,orwindowanddoorhandlesindicatewhethertheyareopenorclosed.Thisconceptcalledambientintelligence,wherehumanshavecomputingandnetworkingtechnologyembeddedintheirsurroundings,wasdevelopedbytheISTAGadvisorygroup.

Whilethisvisionmaysoundutopianwhenyoufirsthearaboutit,currenttechnologyisalreadyatastagewhereitispossibletorealizeit.Ambientintelligencerequiresthattherebethousandsoftinyembeddeddevicesintheenvironment.Eachofthesedevicesrequiresomesourceofpowerforittofunction.Whilepowercanbesenttothemthroughcablesorbatteries,neitherofthesepossibilitiesoffersaneffectiveandlongtermsolution.Thelargenumberofthesedevicesmakesithighlydesirablethattheybefullyself-sustainingandservice-free.Thiscanbeachievedbyharvestingenergyfromtheenvironment.

Energyharvestingisawayofusingtheomnipresentsourcesofenergyinoursurroundings,likefrommovingobjects,vibratingmachineparts,temperaturechanges,electromagneticwavessuchaslight,radioorinfrared.Theideaisnotnew,butsuccessfulandlow-costrealizationinembeddedsystemscallsfortherightexpertise.Aspecificdesignapproachisneededforembeddedsystemsfulfillingtheconceptofambientintelligence.

Words&Expressions

miniaturizationn.小型化,微型化

microprocessorn.微處理器

printcircuit印刷電路

integratevi.融入

surroundingn.環(huán)境

locationsensor定位節(jié)點(diǎn)

communicationmodule通信模塊

environmentn.環(huán)境,外界sewv.縫紉

intelligenthome智能家居

queryvt.詢問

instructionn.指令

ambientintelligence環(huán)境智能

advisoryadj.咨詢的,顧問的

utopianadj.理想化的

self-sustainingadj.自持的

service-freeadj.免維護(hù)的omnipresentadj.無所不在的

vibratingadj.震動的

electromagneticwave電磁波

infraredn.紅外線

expertisen.專門知識

designapproach設(shè)計(jì)方法,設(shè)計(jì)方式13-2-2Exercises

I.Fillineachoftheblankswithoneofthewordsgiveninthefollowinglist,makingchangesifnecessary.

Manages，operatingsystem，embedded，allocation，constraint，kernel，preinstalled，software，storage，similar

Anembeddedoperatingsystem(EOS)issystemsoftwarethat

alltheotherprogramsanddevicesinan

system.Itnormallyguaranteesacertaincapabilitywithinaspecified

sizeandtime

aswellaswithapplicationprograms.Itsstructureisvery

toastructureofanormaloperatingsystemhowevermainlydifferentiatedbysomefactorssuchastypeof

device,functionallimits,takingdesignedjobonly.

Italsonormallyhasbootloader,OS

,requireddevicedrivers,