外文翻译--工程中的微型计算机.doc

英文翻译-1英文翻译资料SystemsUsingMicroprocessorsElectronicsystemsareusedforhandlinginformationinthemostgeneralsense；thisinformationmaybetelephoneconversation,instrumentreadingoracompanysaccounts,butineachcasethesamemaintypesofoperationareinvolved:theprocessing,storageandtransmissionofinformation.Inconventionalelectronicdesigntheseoperationsarecombinedatthefunctionlevel:forexampleacounter,whetherelectronicormechanical,storesthecurrentcountandincrementsitbyoneasrequired.AsystemsuchasanelectronicclockwhichemployscountershasitsstorageandprocessingcapabilitiesspreadthroughoutthesystembecauseeachcounterisabletostoreandProcessnumbers.Presentdaymicroprocessorbasedsystemsdepartfromthisconventionalapproachbyseparatingthethreefunctionsofprocessing,storage,andtransmissionintodifferentsectionofthesystem.ThispartitioningintothreemainfunctionswasdevisedbyVonNeumannduringthe1940s,andwasnotconceivedespeciallyformicrocomputers.Almosteverycomputerevermadehasbeendesignedwiththisstructure,anddespitetheenormousrangeintheirPhysicalforms,theyhaveallbeenofessentiallythesamebasicdesign.InamicroprocerrorbasedsystemtheProcessingwillbeperformedinthemicroprocessorsoitself.Thestoragewillbebymeansofmemorycircuitsandthecommunicationofinformationintoandoutofthesystemwillbebymeansofspecialinput/output(I/O)circuits.Itwouldbeimpossibletoidentifyaparticularpieceofhardwarewhichperformedthecountinginamicroprocessorbasedclockbecausethetimewouldbestoredinthememoryandincrementedatregularintervalsbythemicroprocessor.However,thesoftwarewhichdefinedthesystemsbehaviorwouldcontainsectionsthatperformedascountersTheapparentlyratherabstractapproachtothearchitectureofthemicroprocessoranditsassociatedcircuitsallowsittobeveryflexibleinuse，sincethesystemisdefinedalmostentirelyinsoftwareThedesignprocessislargelyoneofsoftwareengineering,andthesimilarproblemsofconstructionandmaintenancewhichoccurinconventionalengineeringareencounteredwhenproducingsoftware.英文翻译-2Figure15.1illustrateshowthesethreesessionswithinamicrocomputerareconnectedintermsofthecommunicationofinformationwithinthemachineThesystemiscontrolledbythemicroprocessorwhichsupervisesthetransferofinformationbetweenitselfandthememoryandinput/outputsections.Theexternalconnectionsrelatetotherest(thatis，thenon-computerpart)oftheengineeringsystem.Fig.15.1ThreeSectionsofaTypicalMicrocomputerAlthoughonlyonestoragesectionhasbeenshowninthediagram，inpracticetwodistincttypesofmemoryRAMandROMareusedIneachcase，thewordmemoryisratherinappropriatesinceacomputermemoryismorelikeafilingcabinetinconcept；Informationisstoredinasetofnumberedboxesbanditosreferencedbytheserialnumberoftheboxinquestion.MicrocomputersuseRAM(RandomAccessMemoryintowhichdatacanbewrittenandfromwhichdatacanbereadagainwhenneededThisdatacanbereadbackfromthememoryinanysequencedesired,andnotnecessarilythesameorderwhichitwaswritten,hencetheexpressionrandomaccessmemory.AnothertypeofROM(ReadOnlyMemory)isusedtoholdfixedpatternsofinformationwhichcannotbeaffectedbythemicroprocessor；thesepatternsarenotlostwhenpowerisremovedandarenormallyusedtoholdtheProgramwhichdefinesthebehaviorofamicroprocessorbasedsystem.ROMscanbereadlikeRAMs,butunlikeRAMstheycannotbeusedtostorevariableinformation.SomeROMshavetheirdatapatternsputinduringmanufacture,whileothersareprogrammablebytheuserbymeansofspecialequipmentandarecalledProgrammableROMs.ThewidelyusedprogrammableROMsareerasablebymeansofspecialultravioletLampsandarereferredtoasEPROMs，shortforErasableProgrammableReadOnlyMemories.OthernewtypesofdevicecanbeerasedelectricallywithouttheneedforultravioletMemory(RAM,ROM)Micro-ProcessorInput/Output英文翻译-31ight,whicharecalledElectricallyErasableProgrammableReadOnlyMemories,ERPROMs.Themicroprocessorprocessesdataunderthecontroloftheprogram,controllingtheHowofinformationtoandfrommemoryandinput/outputdevices.Someinput/outputdevicesaregeneral-purposetypeswhileothersaredesignedforconktrol1ingspecialhardwaresuchasdiscdrivesorcontrollinginformationtransmissiontoothercomputers.MosttypesofI/0devicesareProgrammabletosomeextent,allowingdifferentmodesofoperation,whilesomeactuallycontainspecial-purposemicroprocesstopermitquitecomplexoperationtobecarriedoutwithoutdirectlyinvolvingthemainmicroprocessor.Themicroprocessor,memoryandinput/outputcircuitmayallbecontainedonthesameintegratedcircuitprovidedthattheapplicationdoesnotrequiretoomuchprogramofdatastorage.Thisisusuallythecaseinlow-costapplicationsuchasthecontrollersusedinmicrowaveovensandautomaticwashingmachines.TheuseofsinglepackageallowsconsiderableseverablecostsavingstobemadewhenarticlesaremanufacturedinlargequantitiesAstechnologydevelops,moreandmorepowerfulprocessorsandlargerandlargeramountsofmemoryarebeingincorporatedintosinglechipmicrocomputerswithresultingsavinginassemblycostsinthefinalproducts.Fortheforeseeablefuture,however,itwillcontinuetobenecessarytointerconnectanumberofintegratedcircuitstomakeamicrocomputerwheneverlargeramountsofstorageorinput/outputarerequired.Anothermajorengineeringapplicationofmicrocomputersisinprocesscontrol.Herethepresenceofthemicrocomputerisusuallymoreapparenttotheuserbecauseprovisionisnormallymadeforprogrammingthemicrocomputerfortheparticularapplication.Inprocesscontrolapplicationsthebenefitsoffittingtheentiresystemontoasinglechipareusuallyoutweighedbythehighdesigncostinvolved,becausethissortofequipmentisproducedinsmallerquantities.Moreover,processcontrollersareusuallymorecomplicatedsothatitismoredifficulttomakethemassingleintegratedcircuits.Twoapproachesarepossible；thecontrollercanbeimplementedasageneral-purposemicrocomputerratherlikeamorerobustversionofahobbycomputer,orasapackagedsystem,heformercasethesystemwouldprobablybeprogrammedinconventionalprogramminglanguage英文翻译-4suchastheonestobeintroducelater,whileintheothercaseaspecial-purposelanguagemightbeused,forexampleonewhichallowedthefunctionofthecontrollertobedescribedintermsofrelayinterconnections.IneithercaseprogramscanbestoredinRAM,whichallowsthemtobealteredtosuitchangesinapplication,butthismakestheoverallsystemvulnerableto1ossofpowerunlessbatteriesareusedtoensurecontinuityofsupply.A1ternativclyprogramscanbestoredinROM,inwhichcasetheyvirtuallybecomepartoftheelectronichardwareandareoftenreferredtoasfirmware.Moresophisticatedprocesscontrollersrequireminicomputersfortheirimplementationalthoughtheuseoflargescaleintegratedcircuitsblursthedistinctionbetweenminiandmicrocomputers.Productsandprocesscontrollerofvariouskindsrepresentthemajorityofpreset-daymicrocomputerapplicators,theexactfiguresdependingononesinterpretationofthewordproduct.Virtuallya11engineeringandscientificusesofmicro-computerscanbeassignedtooneorotherofthesecategories.GeneralElectronicsCircuits1Power-supplyCircuitsMostelectronicequipmentrequiresDCvoltagesforitsoperation.TherecanbeprovidedbybatteriesorinternalpowersuppliesthatconvertalternatingcurrentasavailableatthehomeelectronicoutletintoregulatedDCvoltages.ThefirstelementinaninternalDCpowersupplyisatransformer,whichsteps