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外文翻译--工程中的微型计算机.doc

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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SystemsUsingMicroprocessorsElectronicsystemsareusedforhandlinginformationinthemostgeneralsensethisinformationmaybetelephoneconversation,instrumentreadingoracompanysaccounts,butineachcasethesamemaintypesofoperationareinvolvedtheprocessing,storageandtransmissionofinformation.Inconventionalelectronicdesigntheseoperationsarecombinedatthefunctionlevelforexampleacounter,whetherelectronicormechanical,storesthecurrentcountandincrementsitbyoneasrequired.AsystemsuchasanelectronicclockwhichemployscountershasitsstorageandprocessingcapabilitiesspreadthroughoutthesystembecauseeachcounterisabletostoreandProcessnumbers.Presentdaymicroprocessorbasedsystemsdepartfromthisconventionalapproachbyseparatingthethreefunctionsofprocessing,storage,andtransmissionintodifferentsectionofthesystem.ThispartitioningintothreemainfunctionswasdevisedbyVonNeumannduringthe1940s,andwasnotconceivedespeciallyformicrocomputers.Almosteverycomputerevermadehasbeendesignedwiththisstructure,anddespitetheenormousrangeintheirPhysicalforms,theyhaveallbeenofessentiallythesamebasicdesign.InamicroprocerrorbasedsystemtheProcessingwillbeperformedinthemicroprocessorsoitself.Thestoragewillbebymeansofmemorycircuitsandthecommunicationofinformationintoandoutofthesystemwillbebymeansofspecialinput/outputI/Ocircuits.Itwouldbeimpossibletoidentifyaparticularpieceofhardwarewhichperformedthecountinginamicroprocessorbasedclockbecausethetimewouldbestoredinthememoryandincrementedatregularintervalsbythemicroprocessor.However,thesoftwarewhichdefinedthesystemsbehaviorwouldcontainsectionsthatperformedascounters.Theapparentlyratherabstractapproachtothearchitectureofthemicroprocessoranditsassociatedcircuitsallowsittobeveryflexibleinuse,sincethesystemisdefinedalmostentirelyinsoftware.Thedesignprocessislargelyoneofsoftwareengineering,andthesimilarproblemsofconstructionandmaintenancewhichoccurinconventionalengineeringareencounteredwhenproducingsoftware.英文翻译2Figure15.1illustrateshowthesethreesessionswithinamicrocomputerareconnectedintermsofthecommunicationofinformationwithinthemachine.Thesystemiscontrolledbythemicroprocessorwhichsupervisesthetransferofinformationbetweenitselfandthememoryandinput/outputsections.Theexternalconnectionsrelatetotherestthatis,thenoncomputerpartoftheengineeringsystem.Fig.15.1ThreeSectionsofaTypicalMicrocomputerAlthoughonlyonestoragesectionhasbeenshowninthediagram,inpracticetwodistincttypesofmemoryRAMandROMareused.Ineachcase,thewordmemoryisratherinappropriatesinceacomputermemoryismorelikeafilingcabinetinconceptInformationisstoredinasetofnumberedboxesbanditosreferencedbytheserialnumberoftheboxinquestion.MicrocomputersuseRAMRandomAccessMemoryintowhichdatacanbewrittenandfromwhichdatacanbereadagainwhenneeded.Thisdatacanbereadbackfromthememoryinanysequencedesired,andnotnecessarilythesameorderwhichitwaswritten,hencetheexpressionrandomaccessmemory.AnothertypeofROMReadOnlyMemoryisusedtoholdfixedpatternsofinformationwhichcannotbeaffectedbythemicroprocessorthesepatternsarenotlostwhenpowerisremovedandarenormallyusedtoholdtheProgramwhichdefinesthebehaviorofamicroprocessorbasedsystem.ROMscanbereadlikeRAMs,butunlikeRAMstheycannotbeusedtostorevariableinformation.SomeROMshavetheirdatapatternsputinduringmanufacture,whileothersareprogrammablebytheuserbymeansofspecialequipmentandarecalledProgrammableROMs.ThewidelyusedprogrammableROMsareerasablebymeansofspecialultravioletLampsandarereferredtoasEPROMs,shortforErasableProgrammableReadOnlyMemories.OthernewtypesofdevicecanbeerasedelectricallywithouttheneedforultravioletMemoryRAM,ROMMicroProcessorInput/Output英文翻译31ight,whicharecalledElectricallyErasableProgrammableReadOnlyMemories,ERPROMs.Themicroprocessorprocessesdataunderthecontroloftheprogram,controllingtheHowofinformationtoandfrommemoryandinput/outputdevices.Someinput/outputdevicesaregeneralpurposetypeswhileothersaredesignedforconktrol1ingspecialhardwaresuchasdiscdrivesorcontrollinginformationtransmissiontoothercomputers.MosttypesofI/0devicesareProgrammabletosomeextent,allowingdifferentmodesofoperation,whilesomeactuallycontainspecialpurposemicroprocesstopermitquitecomplexoperationtobecarriedoutwithoutdirectlyinvolvingthemainmicroprocessor.Themicroprocessor,memoryandinput/outputcircuitmayallbecontainedonthesameintegratedcircuitprovidedthattheapplicationdoesnotrequiretoomuchprogramofdatastorage.Thisisusuallythecaseinlowcostapplicationsuchasthecontrollersusedinmicrowaveovensandautomaticwashingmachines.TheuseofsinglepackageallowsconsiderableseverablecostsavingstobemadewhenarticlesaremanufacturedinlargequantitiesAstechnologydevelops,moreandmorepowerfulprocessorsandlargerandlargeramountsofmemoryarebeingincorporatedintosinglechipmicrocomputerswithresultingsavinginassemblycostsinthefinalproducts.Fortheforeseeablefuture,however,itwillcontinuetobenecessarytointerconnectanumberofintegratedcircuitstomakeamicrocomputerwheneverlargeramountsofstorageorinput/outputarerequired.Anothermajorengineeringapplicationofmicrocomputersisinprocesscontrol.Herethepresenceofthemicrocomputerisusuallymoreapparenttotheuserbecauseprovisionisnormallymadeforprogrammingthemicrocomputerfortheparticularapplication.Inprocesscontrolapplicationsthebenefitsoffittingtheentiresystemontoasinglechipareusuallyoutweighedbythehighdesigncostinvolved,becausethissortofequipmentisproducedinsmallerquantities.Moreover,processcontrollersareusuallymorecomplicatedsothatitismoredifficulttomakethemassingleintegratedcircuits.Twoapproachesarepossiblethecontrollercanbeimplementedasageneralpurposemicrocomputerratherlikeamorerobustversionofahobbycomputer,orasapackagedsystem,designedforreplacingcontrollersbaseonoldertechnologiessuchaselectromagneticrelays.intheformercasethesystemwouldprobablybeprogrammedinconventionalprogramminglanguage英文翻译4suchastheonestobeintroducelater,whileintheothercaseaspecialpurposelanguagemightbeused,forexampleonewhichallowedthefunctionofthecontrollertobedescribedintermsofrelayinterconnections.IneithercaseprogramscanbestoredinRAM,whichallowsthemtobealteredtosuitchangesinapplication,butthismakestheoverallsystemvulnerableto1ossofpowerunlessbatteriesareusedtoensurecontinuityofsupply.A1ternativclyprogramscanbestoredinROM,inwhichcasetheyvirtuallybecomepartoftheelectronichardwareandareoftenreferredtoasfirmware.Moresophisticatedprocesscontrollersrequireminicomputersfortheirimplementationalthoughtheuseoflargescaleintegratedcircuitsblursthedistinctionbetweenminiandmicrocomputers.Productsandprocesscontrollerofvariouskindsrepresentthemajorityofpresetdaymicrocomputerapplicators,theexactfiguresdependingononesinterpretationofthewordproduct.Virtuallya11engineeringandscientificusesofmicrocomputerscanbeassignedtooneorotherofthesecategories.GeneralElectronicsCircuits1.PowersupplyCircuitsMostelectronicequipmentrequiresDCvoltagesforitsoperation.TherecanbeprovidedbybatteriesorinternalpowersuppliesthatconvertalternatingcurrentasavailableatthehomeelectronicoutletintoregulatedDCvoltages.ThefirstelementinaninternalDCpowersupplyisatransformer,whichstepsuporstepsdowntheinputvoltagetoalevelsuitablefortheoperationoftheequipment.Asecondaryfunctionofthetransformeristoprovideelectronicgroundinsulationofthedevicefromthepowerlinetoreducepotentialhazards.Arectifier,normallyadiode,thenfollowsthetransformer.Inthepast,vacuumdiodesandawidevarietyofdifferentmaterialssuchasgermaniumcrystalsorcadmiumsulfidewereemployedinthelowpowerrectifiersusedinelectricequipment.Todaysiliconrectifiersareusedalmostexclusivelybecauseoftheirlowcostandhighreliability.FluctuationsandtipplessuperimposedontherectifiedDCvoltagenoticeableasahuminamalfunctioningaudioamplifiercanbefilteredoutbyacapacitor,thelargerthecapacitor,andthesmallertheamountofrippleinthevoltage.Moreprecisecontrolovervoltageslevelsandripplescanbeachievedbyavoltageregulator,which

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