《计算机专业英语》课件第5章

Unit5EmbeddedSystems教学目标教学内容教学目标掌握嵌入式技术的基本概念了解嵌入式技术的的发展简史掌握嵌入式系统的体系结构了解嵌入式技术的应用情况掌握嵌入式软件的体系结构教学内容Text1IntroductionofEmbeddedSystemsText2EmbeddedsoftwarearchitecturesText1IntroductionofEmbeddedSystemsMainContentsWordsandExpressionsExercisesAnembeddedsystemisaspecial-purposecomputersystemdesignedtoperformoneorafewdedicatedfunctions,oftenwithreal-timecomputingconstraints.Itisusuallyembeddedaspartofacompletedeviceincludinghardwareandmechanicalparts.Incontrast,ageneral-purposecomputer,suchasapersonalcomputer,candomanydifferenttasksdependingonprogramming.Embeddedsystemscontrolmanyofthecommondevicesinusetoday.Ingeneral,“embeddedsystem”isnotanexactlydefinedterm,asmanysystemshavesomeelementofprogrammability.Forexample,Handheldcomputerssharesomeelementswithembeddedsystems—suchastheoperatingsystemsandmicroprocessorswhichpowerthem—butarenottrulyembeddedsystems,becausetheyallowdifferentapplicationstobeloadedandperipheralstobeconnected.Embeddedsystemsspanallaspectsofmodernlifeandtherearemanyexamplesoftheiruse.Text1IntroductionofEmbeddedSystemsText1IntroductionofEmbeddedSystemsTelecommunicationssystemsemploynumerousembeddedsystemsfromtelephoneswitchesforthenetworktomobilephonesattheend-user.Computernetworkingusesdedicatedroutersandnetworkbridgestoroutedata.Consumerelectronicsincludepersonaldigitalassistants(PDAs),mp3players,mobilephones,videogameconsoles,digitalcameras,DVDplayers,GPSreceivers,andprinters.Manyhouseholdappliances,suchasmicrowaveovens,washingmachinesanddishwashers,areincludingembeddedsystemstoprovideflexibility,efficiencyandfeatures.AdvancedHVACsystemsusenetworkedthermostatstomoreaccuratelyandefficientlycontroltemperaturethatcanchangebytimeofdayandseason.Homeautomationuseswired-andwireless-networkingthatcanbeusedtocontrollights,climate,security,audio/visual,surveillance,etc.,allofwhichuseembeddeddevicesforsensingandcontrolling.Text1IntroductionofEmbeddedSystemsTransportationsystemsfromflighttoautomobilesincreasinglyuseembeddedsystems.NewairplanescontainadvancedavionicssuchasinertialguidancesystemsandGPSreceiversthatalsohaveconsiderablesafetyrequirements.Variouselectricmotors—brushlessDCmotors,inductionmotorsandDCmotors—areusingelectric/electronicmotorcontrollers.Automobiles,electricvehicles,andhybridvehiclesareincreasinglyusingembeddedsystemstomaximizeefficiencyandreducepollution.Otherautomotivesafetysystemssuchasanti-lockbrakingsystem(ABS),ElectronicStabilityControl(ESC/ESP),tractioncontrol(TCS)andautomaticfour-wheeldrive.Medicalequipmentiscontinuingtoadvancewithmoreembeddedsystemsforvitalsignsmonitoring,electronicstethoscopesforamplifyingsounds,andvariousmedicalimaging(PET,SPECT,CT,MRI)fornon-invasiveinternalinspections.Text1IntroductionofEmbeddedSystemsInadditiontocommonlydescribedembeddedsystemsbasedonsmallcomputers,anewclassofminiaturewirelessdevicescalledmotesarequicklygainingpopularityasthefieldofwirelesssensornetworkingrises.Wirelesssensornetworking,WSN,makesuseofminiaturizationmadepossiblebyadvancedICdesigntocouplefullwirelesssubsystemstosophisticatedsensor,enablingpeopleandcompaniestomeasureamyriadofthingsinthephysicalworldandactonthisinformationthroughITmonitoringandcontrolsystems.Thesemotesarecompletelyselfcontained,andwilltypicallyrunoffabatterysourceformanyyearsbeforethebatteriesneedtobechangedorcharged.WordsandExpressionsreliability[ri,laiə'biliti]n.可靠性portable['pɔ:təbl]adj.轻便的，手提式的stationary['steiʃ(ə)nəri]adj.不动的，稳定的，静止的microcontroller

n.微型控制器，微控制器，单片机peripheral[pə'rifərəl]n.（电脑的）外部设备；adj.不重要的，外围的chassis['ʃæsi]n.底座，（车身）底盘，enclosure[in'kləuʒə]n.附件，围墙，围绕，【计】围封部分programmabilityn.可编程性：减少应用方案的开发时间，降低系统运行和维护成本，提高系统使用效率；handheldadj.手持式，掌上型microprocessor[maikrəʊ'prəʊsesə(r)]n.微处理器flashmemory

n.闪存telecommunication[‘telikəmju:ni’keiʃən]n.电传视讯,远距离通信,电磁通信WordsandExpressionsrouter['ru:tə(r),'raʊ-]n.路由程序,路由器PDA个人数字助理，掌上电脑，是PersonalDigitalAssistant的缩写GPS

即全球定位系统，GlobalPositioningSystem

HVAC（HeatVentilationAirConditionar）暖通空调；HeatingVentilatingandAirConditioning制热、通风与空调控制thermostat['θə:məstæt]n.恒温器，节温器surveillance[sə:'veiləns]n.监视,监督avionics[,eivi'ɔniks]n.航空电子学(航空用电子设备,控制系统)，电子设备inertialguidancesystems

惯性制导系统considerable[kən'sidərəbl]adj.相当的,可观的,重要的hybridvehicle混合驱动汽车，合成车anti-lockbrakingsystem(ABS)防抱死制动系统 WordsandExpressions

electronicstethoscope电子听诊器amplify['æmpli,fai]v.扩大，详述，使...增幅，放大，加强non-invasiveadj.非侵入，非损伤inspection[in'spekʃən]n.检查,视察miniature['minjətʃə]n.缩图,小画像；adj.小规模的,纤小的mote[məut]n.微尘(尘埃,瑕疵)，导火线wirelesssensor无线传感器miniaturization[,miniətʃərai'zeiʃən]n.小型化，微型化sophisticated[sə'fistikeitid]adj.高级的,先进的,复杂的myriad['miriəd]adj.无数的n.极大数量ExercisesI.Trueorfalse?Ifcorrect,writeTinparentheses;Otherwise,writeF.（）1.Anembeddedsystemisaspecial-purposecomputersystemdesignedtoperformonlyonededicatedfunctions,oftenwithreal-timecomputingconstraints.（）2.Ageneral-purposecomputer,suchasapersonalcomputer,candomanydifferenttasksdependingonprogramming.（）3.Sincetheembeddedsystemisdedicatedtospecifictasks,designengineerscanoptimizeit,increasingthesizeandcostoftheproduct,orreducingthereliabilityandperformance.（）4.Ingeneral,“embeddedsystem”isanexactlydefinedterm,asmanysystemshavesomeelementofprogrammability.（）5.Handheldcomputerssharesomeelementswithembeddedsystems—suchastheoperatingsystemsandmicroprocessorswhichpowerthem—butarenottrulyembeddedsystems,becausetheyallowsimilarapplicationstobeloadedandperipheralstobeconnected.（）6.Transportationsystemsfromflighttoautomobilesincreasinglyuseembeddedsystems.NewairplanescontainadvancedavionicssuchasinertialguidancesystemsandPDAsthatalsohaveconsiderablesafetyrequirements.（）7.Homeautomationonlyuseswired-networkingthatcanbeusedtocontrollights,climate,security,audio/visual,surveillance,etc.,allofwhichuseembeddeddevicesforsensingandcontrolling.ExercisesII.Fillintheblankswithproperwords.Anembeddedsystemisa_________computersystemdesignedtoperformoneorafewdedicatedfunctions,oftenwithreal-timecomputingconstraints.2.Physically,embeddedsystemsrangefrom_____devicessuchasdigitalwatchesandMP4players,tolargestationaryinstallationsliketrafficlights,factorycontrollers,orthesystemscontrollingnuclearpowerplants.3.Newairplanescontainadvanced_____suchasinertialguidancesystemsandGPSreceiversthatalsohaveconsiderablesafetyrequirements.4.Automobiles,electricvehicles,andhybridvehiclesareincreasinglyusingembeddedsystemsto_____efficiencyandreducepollution.Text2EmbeddedsoftwarearchitecturesMainContentsWordsandExpressionsExercisesThereareseveraldifferenttypesofsoftwarearchitectureincommonuse.SimplecontrolloopInthisdesign,thesoftwaresimplyhasaloop.Theloopcallssubroutines,eachofwhichmanagesapartofthehardwareorsoftware.InterruptcontrolledsystemSomeembeddedsystemsarepredominantlyinterruptcontrolled.Thismeansthattasksperformedbythesystemaretriggeredbydifferentkindsofevents.Aninterruptcouldbegeneratedforexamplebyatimerinapredefinedfrequency,orbyaserialportcontrollerreceivingabyte.Text2EmbeddedsoftwarearchitecturesText2EmbeddedsoftwarearchitecturesThesekindsofsystemsareusedifeventhandlersneedlowlatencyandtheeventhandlersareshortandsimple.Usuallythesekindsofsystemsrunasimpletaskinamainloopalso,butthistaskisnotverysensitivetounexpecteddelays.Sometimestheinterrupthandlerwilladdlongertaskstoaqueuestructure.Later,aftertheinterrupthandlerhasfinished,thesetasksareexecutedbythemainloop.Thismethodbringsthesystemclosetoamultitaskingkernelwithdiscreteprocesses.CooperativemultitaskingAnonpreemptivemultitaskingsystemisverysimilartothesimplecontrolloopscheme,exceptthattheloopishiddeninanAPI.Theprogrammerdefinesaseriesoftasks,andeachtaskgetsitsownenvironmentto“run”in.Whenataskisidle,itcallsanidleroutine,usuallycalled“pause”,“wait”,“yield”,“nop”(standsfornooperation),etc.Text2EmbeddedsoftwarearchitecturesTheadvantagesanddisadvantagesareverysimilartothecontrolloop,exceptthataddingnewsoftwareiseasier,bysimplywritinganewtask,oraddingtothequeue-interpreter.Preemptivemultitaskingormulti-threadingInthistypeofsystem,alow-levelpieceofcodeswitchesbetweentasksorthreadsbasedonatimer(connectedtoaninterrupt).Thisisthelevelatwhichthesystemisgenerallyconsideredtohavean“operatingsystem”kernel.Dependingonhowmuchfunctionalityisrequired,itintroducesmoreorlessofthecomplexitiesofmanagingmultipletasksrunningconceptuallyinparallel.Asanycodecanpotentiallydamagethedataofanothertask(exceptinlargersystemsusinganMMU)programsmustbecarefullydesignedandtested,andaccesstoshareddatamustbecontrolledbysomesynchronizationstrategy,suchasmessagequeues,semaphoresoranon-blockingsynchronizationscheme.Text2EmbeddedsoftwarearchitecturesBecauseofthesecomplexities,itiscommonfororganizationstobuyareal-timeoperatingsystem,allowingtheapplicationprogrammerstoconcentrateondevicefunctionalityratherthanoperatingsystemservices,atleastforlargesystems;smallersystemsoftencannotaffordtheoverheadassociatedwithagenericrealtimesystem,duetolimitationsregardingmemorysize,performance,and/orbatterylife.Amicrokernelisalogicalstepupfromareal-timeOS.TheusualarrangementisthattheoperatingsystemkernelallocatesmemoryandswitchestheCPUtodifferentthreadsofexecution.Usermodeprocessesimplementmajorfunctionssuchasfilesystems,networkinterfaces,etc.Ingeneral,microkernelssucceedwhenthetaskswitchingandintertaskcommunicationisfast,andfailwhentheyareslow.Exokernelscommunicateefficientlybynormalsubroutinecalls.Thehardware,andallthesoftwareinthesystemareavailableto,andextensiblebyapplicationprogrammers.MicrokernelsandexokernelsMonolithickernelsInthiscase,arelativelylargekernelwithsophisticatedcapabilitiesisadaptedtosuitanembeddedenvironment.ThisgivesprogrammersanenvironmentsimilartoadesktopoperatingsystemlikeLinuxorMicrosoftWindows,andisthereforeveryproductivefordevelopment;onthedownside,itrequiresconsiderablymorehardwareresources,isoftenmoreexpensive,andbecauseofthecomplexityofthesekernelscanbelesspredictableandreliable.CommonexamplesofembeddedmonolithickernelsareEmbeddedLinuxandWindowsCE.Despitetheincreasedcostinhardware,thistypeofembeddedsystemisincreasinginpopularity,especiallyonthemorepowerfulembeddeddevicessuchasWirelessRoutersandGPSNavigationSystems.Herearesomeofthereasons:Portstocommonembeddedchipsetsareavailable.MonolithickernelsTheypermitre-useofpubliclyavailablecodeforDeviceDrivers,WebServers,Firewalls,andothercode.Developmentsystemscanstartoutwithbroadfeature-sets,andthenthedistributioncanbeconfiguredtoexcludeunneededfunctionality,andsavetheexpenseofthememorythatitwouldconsume.Manyengineersbelievethatrunningapplicationcodeinusermodeismorereliable,easiertodebugandthatthereforethedevelopmentprocessiseasierandthecodemoreportable.Manyembeddedsystemslackthetightrealtimerequirementsofacontrolsystem.AsystemsuchasEmbeddedLinuxhasfastenoughresponseformanyapplications.Featuresrequiringfasterresponsethancanbeguaranteedcanoftenbeplacedinhardware.ManyRTOSsystemshaveaper-unitcost.Whenusedonaproductthatisorwillbecomeacommodity,thatcostissignificant.ExoticcustomoperatingsystemsAsmallfractionofembeddedsystemsrequiresafe,timely,reliableorefficientbehaviorunobtainablewiththeoneoftheabovearchitectures.Inthiscaseanorganizationbuildsasystemtosuit.Insomecases,thesystemmaybepartitionedintoa“mechanismcontroller”usingspecialtechniques,anda“displaycontroller”withaconventionaloperatingsystem.Acommunicationsystempassesdatabetweenthetwo.AdditionalsoftwarecomponentsInadditiontothecoreoperatingsystem,manyembeddedsystemshaveadditionalupper-layersoftwarecomponents.ThesecomponentsconsistofnetworkingprotocolstackslikeCAN,TCP/IP,FTP,HTTP,andHTTPS,andalsoincludedstoragecapabilitieslikeFATandFlashmemorymanagementsystems.Iftheembeddeddeviceshasaudioandvideocapabilities,thentheappropriatedriversandcodeswillbepresentinthesystem.Inthecaseofthemonolithickernels,manyofthesesoftwarelayersareincluded.IntheRTOScategory,theavailabilityoftheadditionalsoftwarecomponentsdependsuponthecommercialoffering.WordsandExpressionspredominantly[,pri'dɔminənt]adj.占优势的，支配其他的，优越的，突出的，最显著的，主要的subroutine[,sʌbru:'ti:n]n.子程序，【计算机】=subprogram21世纪大英汉词典》triggered['triɡəd]adj.有触发器的，触发器启动的，有扳机的frequency['fri:kwənsi]n.频繁，频率handler['hændlə]n.处理程序21世纪大英汉词典》latency['leitənsi]n.潜伏，潜在，等待时间queue[kju:]n.【计算机】等候行列，排队nonpreemptiveadj.非抢占式scheme[ski:m]n.方案,计划,阴谋；v.计画,设计,体系，结构,图谋idle['aidl]adj.【机械学】空转的；慢转的；怠速的；【电子学】空载的；无功的routine[ru:'ti:n]n.【计算机】程序；例行程序Interpretern.【计算机】翻译器，译印机，解释程序，翻译程序functionality[,fʌŋkəʃə'næliti]n.函数性(泛函性,官能度),功能（尤指软件、硬件的功能）21世纪大英汉词典》WordsandExpressionsconceptually[kən'septjuəli]adv.概念地21世纪大英汉词典》

parallel['pærəlel]adj.【电子学、计算机】并联的；n.【电子学、计算机】并联的potentially[pə'tenʃəli]adv.潜在地，假定地.MMUabbr.MemoryManagerUnit内存管理单元synchronization[,siŋkrənai'zeiʃən]n.同步化21世纪大英汉词典》

semaphore

['seməfɔ:]n.信号灯,旗语non-blockingadj.非阻塞microkernel微核Shelln.命令解译程序（连接并解译用户命令，调用并执行存储器中的程序）allocate['æləukeit]vi.&vt.【计算机】分配，指定，保留extensible[ik‘stensəbl]adj.可展开的，可伸展的，可延续的；可扩大的，可扩展的；可延伸的WordsandExpressionsdownside['daun,said]n.消极面,负面navigation[,nævi'geiʃən]n.航行,航海guarantee[,gærən'ti:]v.&n.保证,担保；vt.保证RTOSabbr.RealTimeOperatingSystems实时操作系统exotic[,iɡ'zɔtik]adj.1.外来的，非本地的；2.【核物理学】异的；极不稳定的unobtainable['ʌnəb'teinəbl]adj.无法得到的,难获得的partition[pɑ:'tiʃən]n.分割,隔离物,隔墙;v.区分,隔开,分割mechanism['mekənizəm]n.机械,机构,结构,机制，原理upper-layeradj.上层的category['kætigəri]n.种类,类别availability[ə,veilə'biləti]n.有效性；可用性，可得性，利用(或获得)的可能性ExercisesI.Trueorfalse?Ifcorrect,writeTinparentheses;Otherwise,writeF.（）1.Theloopcallssubroutines,eachofwhichmanagesallofthehardwareorsoftware.（）2.Thisgivesprogrammersanenvironmentdifferenttoa