会员注册 | 登录 | 微信快捷登录 支付宝快捷登录 QQ登录 微博登录 | 帮助中心 人人文库renrendoc.com美如初恋!
站内搜索 百度文库

热门搜索: 直缝焊接机 矿井提升机 循环球式转向器图纸 机器人手爪发展史 管道机器人dwg 动平衡试验台设计

   首页 人人文库网 > 资源分类 > DOC文档下载

外文翻译--单片机系统.doc

  • 资源星级:
  • 资源大小:64.50KB   全文页数:7页
  • 资源格式: DOC        下载权限:注册会员/VIP会员
您还没有登陆,请先登录。登陆后即可下载此文档。
  合作网站登录: 微信快捷登录 支付宝快捷登录   QQ登录   微博登录
友情提示
2:本站资源不支持迅雷下载,请使用浏览器直接下载(不支持QQ浏览器)
3:本站资源下载后的文档和图纸-无水印,预览文档经过压缩,下载后原文更清晰   

外文翻译--单片机系统.doc

附录2MicrocomputerSystemsElectronicsystemsareusedforhandinginformationinthemostgeneralsensethisinformationmaybetelephoneconversation,instrumentreadoracompanysaccounts,butineachcasethesamemaintypeofoperationareinvolvedtheprocessing,storageandtransmissionofinformation.inconventionalelectronicdesigntheseoperationsarecombinedatthefunctionlevelforexampleacounter,whetherelectronicormechanical,storesthecurrentandincrementsitbyoneasrequired.Asystemsuchasanelectronicclockwhichemployscountershasitsstorageandprocessingcapabilitiesspreadthroughoutthesystembecauseeachcounterisabletostoreandprocessnumbers.Presentdaymicroprocessorbasedsystemsdepartfromthisconventionalapproachbyseparatingthethreefunctionsofprocessing,storage,andtransmissionintodifferentsectionofthesystem.ThispartitioningintothreemainfunctionswasdevisedbyVonNeumannduringthe1940s,andwasnotconceivedespeciallyformicrocomputers.Almosteverycomputerevermadehasbeendesignedwiththisstructure,anddespitetheenormousrangeintheirphysicalforms,theyhaveallbeenofessentiallythesamebasicdesign.Inamicroprocessorbasedsystemtheprocessingwillbeperformedinthemicroprocessoritself.Thestoragewillbebymeansofmemorycircuitsandthecommunicationofinformationintoandoutofthesystemwillbebymeansofspecialinput/outputI/Ocircuits.Itwouldbeimpossibletoidentifyaparticularpieceofhardwarewhichperformedthecountinginamicroprocessorbasedclockbecausethetimewouldbestoredinthememoryandincrementedatregularintervalsbutthemicroprocessor.However,thesoftwarewhichdefinedthesystemsbehaviorwouldcontainsectionsthatperformedascounters.Theapparentlyratherabstractapproachtothearchitectureofthemicroprocessoranditsassociatedcircuitsallowsittobeveryflexibleinuse,sincethesystemisdefinedalmostentirelysoftware.Thedesignprocessislargelyoneofsoftwareengineering,andthesimilarproblemsofconstructionandmaintenancewhichoccurinconventionalengineeringareencounteredwhenproducingsoftware.Thefigure1.1illustrateshowthesethreesectionswithinamicrocomputerareconnectedintermsofthecommunicationofinformationwithinthemachine.Thesystemiscontrolledbythemicroprocessorwhichsupervisesthetransferofinformationbetweenitselfandthememoryandinput/outputsections.Theexternalconnectionsrelatetotherestthatis,thenoncomputerpartoftheengineeringsystem.Fig.1.1ThreeSectionsofaTypicalMicrocomputerAlthoughonlyonestoragesectionhasbeenshowninthediagram,inpracticetwodistincttypesofmemoryRAMandROMareused.Ineachcase,thewordmemoryisratherinappropriatesinceacomputersmemoryismorelikeafilingcabinetinconceptinformationisstoredinasetofnumberedboxesanditisreferencedbytheserialnumberoftheboxinquestion.MicrocomputersuseRAMRandomAccessMemoryintowhichdatacanbewrittenandfromwhichdatacanbereadagainwhenneeded.Thisdatacanbereadbackfromthememoryinanysequencedesired,andnotnecessarilythesameorderinwhichitwaswritten,hencetheexpressionrandomaccessmemory.AnothertypeofROMReadOnlyMemoryisusedtoholdfixedpatternsofinformationwhichcannotbeaffectedbythemicroprocessorthesepatternsarenotlostwhenpowerisremovedandarenormallyusedtoholdtheprogramwhichdefinesthebehaviorofamicroprocessorbasedsystem.ROMscanbereadlikeRAMs,butunlikeRAMstheycannotbeusedtostorevariableinformation.SomeROMshavetheirdatapatternsputinduringmanufacture,whileothersareprogrammablebytheuserbymeansofspecialequipmentandarecalledprogrammableROMs.ThewidelyusedprogrammableROMsareerasablebymeansofspecialultravioletlampsandarereferredtoasEPROMs,shortforErasableProgrammableReadOnlyMemories.Othernewtypesofdevicecanbeerasedelectricallywithouttheneedforultravioletlight,whicharecalledElectricallyErasableProgrammableReadOnlyMemories,EEPROMs.Themicroprocessorprocessesdataunderthecontroloftheprogram,controllingtheflowofinformationtoandfrommemoryandinput/outputdevices.Someinput/outputdevicesaregeneralpurposetypeswhileothersaredesignedforcontrollingspecialhardwaresuchasdiscdrivesorcontrollinginformationtransmissiontoothercomputers.MosttypesofI/Odevicesareprogrammabletosomeextent,allowingdifferentmodesofoperation,whilesomeactuallycontainspecialpurposemicroprocessorstopermitquitecomplexoperationstobecarriedoutwithoutdirectlyinvolvingthemainmicroprocessor.Themicroprocessorprocessesdataunderthecontroloftheprogram,controllingtheflowofinformationtoandfrommemoryandinput/outputdevices.Someinput/outputdevicesaregeneralpurposetypeswhileothersaredesignedforcontrollingspecialhardwaresuchasdiscdrivesorcontrollinginformationtransmissiontoothercomputers.MosttypesofI/Odevicesareprogrammabletosomeextent,allowingdifferentmodesofoperation,whilesomeactuallycontainspecialpurposemicroprocessorstopermitquitecomplexoperationstobecarriedoutwithoutdirectlyinvolvingthemainmicroprocessor.Themicroprocessor,memoryandinput/outputcircuitmayallbecontainedonthesameintegratedcircuitprovidedthattheapplicationdoesnotrequiretoomuchprogramordatastorage.Thisisusuallythecaseinlowcostapplicationsuchasthecontrollersusedinmicrowaveovensandautomaticwashingmachines.Theuseofsinglepackageallowsconsiderablecostsavingstoemadewhenarticlesaremanufacturedinlargequantities.Astechnologydevelops,moreandmorepowerfulprocessorsandlargerandlargeramountsofmemoryarebeingincorporatedintosinglechipmicrocomputerswithresultingsavinginassemblycostsinthefinalproducts.Fortheforeseeablefuture,however,itwillcontinuetobenecessarytointerconnectanumberofintegratedcircuitstomakeamicrocomputerwheneverlargeramountsofstorageorinput/outputarerequired.Anothermajorengineeringapplicationofmicrocomputersisinprocesscontrol.Herethepresenceofthemicrocomputerisusuallymoreapparenttotheuserbecauseprovisionisnormallymadeforprogrammingthemicrocomputerfortheparticularapplication.Inprocesscontrolapplicationsthebenefitslffittingtheentiresystemontosinglechipareusuallyoutweighedbythehighdesigncostinvolved,becausethissortlfequipmentisproducedinsmallerquantities.Moreover,processcontrollersareusuallymorecomplicatedsothatitismoredifficulttomakethemassingleintegratedcircuits.Twoapproachesarepossiblethecontrollercanbeimplementedasageneralpurposemicrocomputerratherlikeamorerobustversionlfahobbycomputer,orasapackagedsystem,signedforreplacingcontrollersbasedonoldertechnologiessuchaselectromagneticrelays.Intheformercasethesystemwouldprobablybeprogrammedinconventionalprogramminglanguagessuchastheonesto9beintroducedlater,whileintheothercaseaspecialpurposelanguagemightbeused,forexampleonewhichallowedthefunctionofthecontrollertobedescribedintermsofrelayinterconnections,IneithercaseprogramscanbestoredinRAM,whichallowsthemtobealteredtosuitchangesinapplication,butthismakestheoverallsystemvulnerabletolosslfpowerunlessbatteriesareusedtoensurecontinuityofsupply.AlternativelyprogramscanbestoredinROM,inwhichcasetheyvirtuallybecomepartoftheelectronichardwareandareoftenreferredtoasfirmware.Moresophisticatedprocesscontrollersrequireminicomputersfortheirimplementation,althoughtheuselflargescaleintegratedcircuitsthedistinctionbetweenminiandmicrocomputers,Productsandprocesscontrollersofvariouskindsrepresentthemajorityofpresentdaymicrocomputerapplications,theexactfiguresdependingononesinterpretationofthewordproduct.Virtuallyallengineeringandscientificusesofmicrocomputerscanbeassignedtooneorotherofthesecategories.ButinthesystemwemoststudyPressureandPressureTransmitters.Pressureariseswhenaforceisappliedoveranarea.ProvidedtheforceisoneNewtonanduniformlyovertheareaofonesquaremeters,thepressurehasbeendesignatedonePascal.Pressureisauniversalprocessingcondition.Itisalsoaconditionoflifeontheplanetweliveatthebottomofanatmosphericoceanthatextendsupwardformanymiles.Thismassofairhasweight,andthisweightpressingdownwardcausesatmosphericpressure.Water,afundamentalnecessityoflife,issuppliedtomostofusunderpressure.Inthetypicalprocessplant,pressureinfluencesboilingpointtemperatures,condensingpointtemperatures,processefficiency,costs,andotherimportantfactors.Themeasurementandcontrolofpressureorlackofitvacuuminthetypicalprocessplantiscritical.Theworkinginstrumentsintheplantusuallyincludesimplepressuregauges,precisionrecordersandindicators,andpneumaticandelectronicpressuretransmitters.Apressuretransmittermakesapressuremeasurementandgenerateseitherapneumaticorelectricalsignaloutputthatisproportionaltothepressurebeingsensed.Intheprocessplant,itisimpracticaltolocatethecontrolinstrumentsoutintheplaceneartheprocess.Itisalsotruethatmostmeasurementsarenoteasilytransmittedfromsomeremotelocation.Pressuremeasurementisanexception,butifahighpressureofsomedangerouschemicalistobeindicatedorrecordedseveralhundredfeetfromthepointofmeasurement,ahazardmaybefromthepressureorfromthechemicalcarried.Toeliminatethisproblem,asignaltransmissionsystemwasdeveloped.Thissystemisusuallyeitherpneumaticorelectrical.Andcontrolinstrumentsinonelocation.Thismakesitpracticalforaminimumnumberofoperatorstoruntheplantefficiently.Whenapneumatictransmissionsystemisemployed,themeasurementsignalisconvertedintopneumaticsignalbythetransmitterscaledfrom0to100percentofthemeasurementvalue.Thistransmitterismountedclosetothepointofmeasurementintheprocess.Thetransmitteroutputairpressureforapneumatictransmitterispipedtotherecordingorcontrolinstrument.Thestandardoutputrangeforapneumatictransmitteris20to100kPa,whichisalmostuniversallyused.Whenanelectronicpressuretransmitterisused,thepressureisconvertedtoelectricalsignalthatmaybecurrentorvoltage.Itsstandardrangeisfrom4to20mADCforcurrentsignalorfrom1to5VDCforvoltagesignal.Nowadays,anothertypeofelectricalsignal,whichisbecomingcommon,isthedigitalordiscretesignal.Theuseofinstrumentsandcontrolsystemsbasedoncomputerorforcingincreaseduseofthistypeofsignal.Sometimesitisimportantforanalysistoobtaintheparametersthatdescribethesensor/transmitterbehavior.Thegainisfairlysimpletoobtainoncethespanisknown.Consideranelectronicpressuretransmitterwitharangeof0~600kPa.Thegainisdefinedasthechangeinoutputdividedbythechangeininput.Inthiscase,theoutputiselectricalsignal4~20mADCandtheinputisprocesspressure0~600kPa.Thusthegain.BesidewemustmeasureTemperatureTemperaturemeasurementisimportantinindustrialcontrol,asdirectindicationsofsystemorproductstateandasindirectindicationsofsuchfactorsasreactionrates,energyflow,turbineefficiency,andlubricantquality.Presenttemperaturescaleshavebeeninuseforabout200years,theearliestinstrumentswerebasedonthethermalexpansionofgasesandliquids.Suchfilledsystemsarestillemployed,althoughmanyothertypesofinstrumentsareavailable.Representativetemperaturesensorsincludefilledthermalsystems,liquidinglassthermometers,thermocouples,resistancetemperaturedetectors,thermostats,bimetallicdevices,opticalandradiationpyrometersandtemperaturesensitivepaints.Advantagesofelectricalsystemsincludehighaccuracyandsensitivity,practicalityofswitchingorscanningseveralmeasurementspoints,largerdistancespossiblebetweenmeasuringelementsandcontrollers,replacementofcomponentsratherthancompletesystem,fastresponse,andabilitytomeasurehighertemperature.Amongtheelectricaltemperaturesensors,thermocouplesandresistancetemperaturedetectorsaremostwidelyused.kPamAkPamAkPakPamAmAKr027.0600160600420

注意事项

本文(外文翻译--单片机系统.doc)为本站会员(英文资料库)主动上传,人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对上载内容本身不做任何修改或编辑。 若此文所含内容侵犯了您的版权或隐私,请立即通知人人文库网([email protected]),我们立即给予删除!

温馨提示:如果因为网速或其他原因下载失败请重新下载,重复下载不扣分。

copyright@ 2015-2017 人人文库网网站版权所有
苏ICP备12009002号-5