外文翻译--工程中的单片机.doc

徐州工程学院毕业设计(论文)1附录附录1英文翻译MicroprocessorsinEngineersThedevelopmentofthemicroprocessorduringthe1970sbroughtaboutarevolutioninengineeringdesign.Theindustrialrevolutionattheturnofthenineteenthcenturyheraldedthedevelopmentofthemachineswhichcouldreplacephysicaldrudgerybymechanicalmeans.Apartfromafewexceptions,however,thesemachinesrequiredmanualsupervisionbecausetheproblemofcontrollingthismechanicalpowerwasnotatallstraightforward.Manytypesofautomaticcontrolsystemshaveappearedduringthetwentiethcentury,basedonelectronic,mechanical,hydraulicandfluidicprinciples.Ineachcasethedesigntechniqueshavebeensimilarbecauseeachcomponentofthesystemusuallycontributesasinglewelldefinedfunctiontothesystembehavior.Themicroprocessorrepresentsafundamentallydifferentapproachtothedesignofasystem.Itsphysicalformisquitesimpleandreliable,consistingofafewgeneral-purposeelementswhichcanbeprogrammedtomakethesystemfunctionasrequired.Itisthecontrollingprogramwhichmustbedesignedtogivethesystemtherequiredbehavior,andwhichwillcontain“components”and“subassemblies”justlikeanyotherkindofengineering.Theprogram,orsoftware,isjustoftheengineeredsystemasthephysicalhardware,butitismuchlesssusceptibletofailure,providedthatitisdesignedproperly.Theideaofprogrammedsystemsisnotnew；electroniccomputershavebeeninexistenceformanydecades.However,ithastakenthedevelopmentofthelargescaleintegratedcircuit-thesiliconchip-toproducecomputerswhicharecheap,rugged,andreliableenoughtobeincorporatedintoengineeringdesignsascomponents.Thetechniquesofsoftwaredesignarewellknowntocomputerscientistsanditisnotsurprisingthattheprinciplesofgoodengineeringdesignand“softwareengineering”areessentiallythoseofgoodengineeringdesign.Weshallseethatengineeringdesignusingsoftwareallowssystemstobedesignedmoreeasilythanusingmoreconventionaltechniques.Itisthecombinationofdevelopmentsinelectronicdevicetechnologywiththoseincomputertechnologywhichhasenabledthemicroprocessortobeproduced,andthesetechnologieshave“converged”toproducethemicro-electronicindustrywhichweseetoday.Morerecentdevelopmentsinintegratedcircuittechnologyhaveledtotheintroductionofmicroprocessorsmallcomputersfabricatedusingrelativelyfewintegratedcircuitcomponents.In徐州工程学院毕业设计(论文)2factanentiremicroprocessorcanbemadeasasinglechip.AttheheartofanycomputerisaCentralProcessingUnitorCPU,andthecorrespondingheartofthemicroprocessorisMPU(Micro-ProcessorUnit),whichissimplyaCPUimplementedonasiliconchip.Itsprocessingpowerisgreaterthanthatofitsgiantpredecessorsandyetitischeapandrobustenoughtobetreatedassimplyanotherengineeringcomponent.Themicroprocessorwasconceivedasadevicewhichcouldbeprogrammedinaveryflexiblefashiontogivealmostanydesiredbehaviorbymeansofalistofelectronicinstructions.Usingamicroprocessorinvolvesprogrammingskillinproducingtheselistsofinstructionsaswellasmoreconventionalelectronicandmechanicaldesigntechniques.Asitsnamesuggests,themicroprocessorisorganizedinmuchthesamewayasaconventionalcomputer；indeed,itmayberegardedasthe“natural”outcomeofthe“evolution”ofthecomputerfromitsearliestdays.SystemsUsingMicroprocessorsElectronicsystemsareusedforhandlinginformationinthemostgeneralsense；thisinformationmaybetelephoneconversation,instrumentreadingoracompanysaccounts,butineachcasethesamemaintypesofoperationareinvolved:theprocessing,storageandtransmissionofinformation.Inconventionalelectronicdesigntheseoperationsarecombinedatthefunctionlevel:forexampleacounter,whetherelectronicormechanical,storesthecurrentcountandincrementsitbyoneasrequired.Asystemsuchasanelectronicclockwhichemployscountershasitsstorageandprocessingcapabilitiesspreadthroughoutthesystembecauseeachcounterisabletostoreandprocessnumbers.Presentdaymicroprocessorbasedsystemsdepartfromthisconventionalapproachbyseparatingthethreefunctionsofprocessing,storage,andtransmissionintodifferentsectionsofthesystem.ThispartitioningintothreemainfunctionswasdevisedbyVonNeumannduringthe1940s,andwasnotconceivedespeciallyformicrocomputers.Almosteverycomputerevermadehasbeendesignedwiththisstructure,anddespitetheenormousrangeintheirphysicalforms,theyhaveallbeenofessentiallythesamebasicdesign.Inamicroprocessorbasedsystemtheprocessingwillbeperformedinthemicroprocessoritself.Thestoragewillbebymeansofmemorycircuitsandthecommunicationofinformationintoandoutofthesystemwillbebymeansofspecialinput/output(I/O)circuits.Itwouldbeimpossibletoidentifyaparticularpieceofhardwarewhichperformedthecountinginamicroprocessorbasedclockbecausethetimewouldbestoredinthememoryandincrementedatregularintervalsbythemicroprocessor.However,thesoftwarewhichdefinedthesystemsbehaviorwouldcontainsectionsthatperformedascounters.Theapparentlyratherabstract徐州工程学院毕业设计(论文)3approachtothearchitectureofthemicroprocessoranditsassociatedcircuitsallowsittobeveryflexibleinuse,sincethesystemisdefinedalmostentirelyinsoftware.Thedesignprocessislargelyoneofsoftwareengineering,andthesimilarproblemsofconstructionandmaintenancewhichoccurinconventionalengineeringareencounteredwhenproducingsoftware.Howthesethreesectionswithinamicrocomputerareconnectedintermsofthecommunicationofinformationwithinthemachine.Thesystemiscontrolledbythemicroprocessorwhichsupervisesthetransferofinformationbetweenitselfandthememoryandinput/outputsections.Theexternalconnectionsrelatetotherest(thatis,thenon-computerpart)oftheengineeringsystem.Althoughonlyonestoragesectionhasbeenshowninthediagram,inpracticetwodistincttypesofmemoryRAMandROMareused.Ineachcase,thewordmemoryisratherinappropriatesinceacomputermemoryismorelikeafilingcabinetinconcept；informationisstoredinasetofnumberedboxesanditisreferencedbytheserialnumberoftheboxinquestion.MicrocomputersuseRAM(RandomAccessMemory)intowhichdatacanbewrittenandfromwhichdatacanbereadagainwhenneeded.Thisdatacanbereadbackfromthememoryinanysequencedesired,andnotnecessarilythesameorderinwhichitwaswritten,hencetheexpressionrandomaccessmemory.AnothertypeofROM(ReadOnlyMemory)isusedtoholdfixedpatternsofinformationwhichcannotbeaffectedbythemicroprocessor；thesepatternsarenotlostwhenpowerisremovedandarenormallyusedtoholdtheprogramwhichdefinesthebehaviorofamicroprocessorbasedsystem.ROMscanbereadlikeRAMS,butunlikeRAMStheycannotbeusedtostorevariableinformation.SomeROMshavetheirdatapatternsputinduringmanufacture,whileothersareprogrammablebytheuserbymeansofspecialequipmentandarecalledprogrammableROMs.ThewidelyusedprogrammableROMsareerasablebymeansofspecialultravioletlampsandarereferredtoasEPROMS,shortforErasableProgrammableReadOnlyMemories.Othernewtypesofdevicecanbeerasedelectricallywithouttheneedforultravioletlight,whicharecalledElectricallyErasableProgrammableReadOnlyMemories,EEPROMS.Themicroprocessorprocessesdataunderthecontroloftheprogram,controllingtheflowofinformationtoandfrommemoryandinput/outputdevices.Someinput/outputdevicesaregeneral-purposetypeswhileothersaredesignedforcontrollingspecialhardwaresuchasdiscdrivesorcontrollinginformationtransmissiontoothercomputers.MosttypesofI/Odevicesareprogrammabletosomeextent,allowingdifferentmodesofoperation,whilesomeactuallycontainspecial-purposemicroprocessorstopermitquitecomplexoperationstobecarriedoutwithoutdirectlyinvolvingthemainmicroprocessor.徐州工程学院毕业设计(论文)4Themicroprocessor,memoryandinput/outputcircuitmayallbecontainedonthesameintegratedcircuitprovidedthattheapplicationdoesnotrequiretoomuchprogramordatastorage.Thisisusuallythecaseinlow-costapplicationsuchasthecontrollersusedinmicrowaveovensandautomaticwashingmachines.Theuseofsinglepackageallowsconsiderablecostsavingstobemadewhenarticlesaremanufacturedinlargequantities.Astechnologydevelops,moreandmorepowerfulprocessorsandlargerandlargeramountsofmemoryarebeingincorporatedintosinglechipmicrocomputerswithresultingsavinginassemblycostsinthefinalproducts.Fortheforeseeablefuture,however,itwillcontinuetobenecessarytointerconnectanumberofintegratedcircuitstomakeamicrocomputerwheneverlargeramountsofstorageorinput/outputarerequired.Anothermajorengineeringapplicationofmicrocomputersisinprocesscontrol.Herethepresenceofthemicrocomputerisusuallymoreapparenttotheuserbecauseprovisionisnormallymadeforprogrammingthemicrocomputerfortheparticularapplication.Inprocesscontrolapplicationsthebenefitsoffittingtheentiresystemontoasinglechipareusuallyoutweighedbythehighdesigncostinvolved,becausethissortofequipmentisproducedinsmallerquantities.Moreover,processcontrollersareusuallymorecomplicatedsothatitismoredifficulttomakethemassingleintegratedcircuits.Twoapproachesarepossible；thecontrollercanbeimplementedasageneral-purposemicrocomputerratherlikeamorerobustversionofahobbycomputer,orasapackagedsystem,designedforreplacingcontrollersbasedonoldertechnologiessuchaselectromagneticrelays.Intheformercasethesystemwouldprobablybeprogrammedinconventionalprogramminglanguagessuchastheonestobeintroducedlater,whileintheothercaseaspecial-purposelanguagemightbeused,forexampleonewhichallowedthefunctionofthecontrollertobedescribedintermsofrelayinterconnections.IneithercaseprogramscanbestoredinRAM,whichallowsthemtobealteredtosuitchangesinapplication,butthismakestheoverallsystemvulnerabletolossofpowerunlessbatteriesareusedtoensurecontinuityofsupply.AlternativelyprogramscanbestoredinROM,inwhichcasetheyvirtuallybecomepartoftheelectronichardwareandareoftenreferredtoasfirmware.Moresophisticatedprocesscontrollersrequireminicomputersfortheirimplementation,althoughtheuseoflargescaleintegratedcircuitsblursthedistinctionbetweenmini-andmicrocomputers.Productsandprocesscontrollersofvariouskindsrepresentthemajorityofpresent-daymicrocomputerapplications,theexactfiguresdependingononesinterpretationofthewordproduct.Virtuallyallengineeringandscientificusesofmicrocomputerscanbeassignedtooneorotherofthesecategories.MicrocomputerInterface