外文以及翻译-基于单片机的电子琴设计.docx

外文以及翻译-基于单片机的电子琴设计.docx

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外文资料原文

Microcontroller-baseddesignandmanufacture

（1）MCU

Amicrocontroller（orMCU）isacomputer-on-a-chip.Itisatypeofmicroprocessoremphasizingself-sufficiencyandcost-effectiveness,incontrasttoageneral-purposemicroprocessor（thekindusedinaPC）.

Themajorityofcomputersystemsinusetodayareembeddedinothermachinery,suchastelephones,clocks,appliances,vehicles,andinfrastructure.Anembeddedsystemusuallyhasminimalrequirementsformemoryandprogramlengthandmayrequiresimplebutunusualinput/outputsystems.Forexample,mostembeddedsystemslackkeyboards,screens,disks,printers,orotherrecognizableI/Odevicesofapersonalcomputer.Theymaycontrolelectricmotors,relaysorvoltages,andreadswitches,variableresistorsorotherelectronicdevices.Often,theonlyI/Odevicereadablebyahumanisasinglelight-emittingdiode,andseverecostorpowerconstraintscaneveneliminatethat.

Incontrasttogeneral-purposeCPUs,microcontrollersdonothaveanaddressbusoradatabus,becausetheyintegratealltheRAMandnon-volatilememoryonthesamechipastheCPU.Becausetheyneedfewerpins,thechipcanbeplacedinamuchsmaller,cheaperpackage.

Integratingthememoryandotherperipheralsonasinglechipandtestingthemasaunitincreasesthecostofthatchip,butoftenresultsindecreasednetcostoftheembeddedsystemasawhole.（EvenifthecostofaCPUthathasintegratedperipheralsisslightlymorethanthecostofaCPU+externalperipherals,havingfewerchipstypicallyallowsasmallerandcheapercircuitboard,andreducesthelaborrequiredtoassembleandtestthecircuitboard）.Thistrendleadstodesign.

Amicrocontrollerisasingleintegratedcircuit,commonlywiththefollowingfeatures:

centralprocessingunit-rangingfromsmallandsimple4-bitprocessorstosophisticated32-or64-bitprocessors

input/outputinterfacessuchasserialports（UARTs）

otherserialcommunicationsinterfaceslikePC,SerialPeripheralInterfaceandControllerAreaNetworkforsysteminterconnectperipheralssuchastimersandwatchdogRAMfordatastorageROM,EPROM,EEPROMorFlashmemoryforprogramstorageclockgenerator-oftenanoscillatorforaquartztimingcrystal,resonatororRCcircuitmanyincludeanalog-to-digitalconverters.

ThisintegrationdrasticallyreducesthenumberofchipsandtheamountofwiringandPCBspacethatwouldbeneededtoproduceequivalentsystemsusingseparatechipsandhaveprovedtobehighlypopularinembeddedsystemssincetheirintroductioninthe1970s.

SomemicrocontrollerscanaffordtouseaHarvardarchitecture:

separatememorybusesforinstructionsanddata,allowingaccessestotakeplaceconcurrently.

Thedecisionofwhichperipheraltointegrateisoftendifficult.TheMicrocontrollervendorsoftentradeoperatingfrequenciesandsystemdesignflexibilityagainsttime-to-marketrequirementsfromtheircustomersandoveralllowersystemcost.Manufacturershavetobalancetheneedtominimizethechipsizeagainstadditionalfunctionality.

Microcontrollerarchitecturesareavailablefrommanydifferentvendorsinsomanyvarietiesthateachinstructionsetarchitecturecouldrightlybelongtoacategoryoftheirown.Chiefamongthesearethe8051,Z80andARMderivatives.[citationneeded]

Amicrocontroller（alsoMCUorpC）isafunctionalcomputersystem-on-a-chip.Itcontainsaprocessorcore,memory,andprogrammableinput/outputperipherals.

MicrocontrollersincludeanintegratedCPU,memory（asmallamountofRAM,programmemory,orboth）andperipheralscapableofinputandoutput.

Itemphasizeshighintegration,incontrasttoamicroprocessorwhichonlycontainsaCPU（thekindusedinaPC）.Inadditiontotheusualarithmeticandlogicelementsofageneralpurposemicroprocessor,themicrocontrollerintegratesadditionalelementssuchasread-writememoryfordatastorage,read-onlymemoryforprogramstorage,Flashmemoryforpermanentdatastorage,peripherals,andinput/outputinterfaces.Atclockspeedsofaslittleas32KHz,microcontrollersoftenoperateatverylowspeedcomparedtomicroprocessors,butthisisadequatefortypicalapplications.Theyconsumerelativelylittlepower（milliwattsorevenmicrowatts）,andwillgenerallyhavetheabilitytoretainfunctionalitywhilewaitingforaneventsuchasabuttonpressorinterrupt.Powerconsumptionwhilesleeping（CPUclockandperipheralsdisabled）maybejustnanowatts,makingthemidealforlowpowerandlonglastingbatteryapplications.

Microcontrollersareusedinautomaticallycontrolledproductsanddevices,suchasautomobileenginecontrolsystems,remotecontrols,officemachines,appliances,powertools,andtoys.Byreducingthesize,cost,andpowerconsumptioncomparedtoadesignusingaseparatemicroprocessor,memory,andinput/outputdevices,microcontrollersmakeiteconomicaltoelectronicallycontrolmanymoreprocesses.

Themajorityofcomputersystemsinusetodayareembeddedinothermachinery,suchasautomobiles,telephones,appliances,andperipheralsforcomputersystems.Thesearecalledembeddedsystems.Whilesomeembeddedsystemsareverysophisticated,manyhaveminimalrequirementsformemoryandprogramlength,withnooperatingsystem,andlowsoftwarecomplexity.Typicalinputandoutputdevicesincludeswitches,relays,solenoids,LEDs,smallorcustomLCDdisplays,radiofrequencydevices,andsensorsfordatasuchastemperature,humidity,lightleveletc.Embeddedsystemsusuallyhavenokeyboard,screen,disks,printers,orotherrecognizableI/Odevicesofapersonalcomputer,andmaylackhumaninteractiondevicesofanykind.

Itismandatorythatmicrocontrollersproviderealtimeresponsetoeventsintheembeddedsystemtheyarecontrolling.Whencertaineventsoccur,aninterruptsystemcansignaltheprocessortosuspendprocessingthecurrentinstructionsequenceandtobeginaninterruptserviceroutine（ISR）.TheISRwillperformanyprocessingrequiredbasedonthesourceoftheinterruptbeforereturningtotheoriginalinstructionsequence.Possibleinterruptsourcesaredevicedependent,andoftenincludeeventssuchasaninternaltimeroverflow,completingananalogtodigitalconversion,alogiclevelchangeonaninputsuchasfromabuttonbeingpressed,anddatareceivedonacommunicationlink.Wherepowerconsumptionisimportantasinbatteryoperateddevices,interruptsmayalsowakeamicrocontrollerfromalowpowersleepstatewheretheprocessorishalteduntilrequiredtodosomethingbyaperipheralevent.

Microcontrollerprogramsmustfitintheavailableon-chipprogrammemory,sinceitwouldbecostlytoprovideasystemwithexternal,expandable,memory.Compilersandassemblylanguageareusedtoturnhigh-levellanguageprogramsintoacompactmachinecodeforstorageinthemicrocontroller'smemory.Dependingonthedevice,theprogrammemorymaybepermanent,read-onlymemorythatcanonlybeprogrammedatthefactory,orprogrammemorymaybefield-alterableflashorerasableread-onlymemory.

Sinceembeddedprocessorsareusuallyusedtocontroldevices,theysometimesneedtoacceptinputfromthedevicetheyarecontrolling.Thisisthepurposeoftheanalogtodigitalconverter.Sinceprocessorsarebuilttointerpretandprocessdigitaldata,i.e.IsandOs,theywon'tbeabletodoanythingwiththeanalogsignalsthatmaybebeingsenttoitbyadevice.Sotheanalogtodigitalconverterisusedtoconverttheincomingdataintoaformthattheprocessorcanrecognize.Thereisalsoadigitaltoanalogconverterthatallowstheprocessortosenddatatothedeviceitiscontrolling.

Inadditiontotheconverters,manyembeddedmicroprocessorsincludeavarietyoftimersaswell.OneofthemostcommontypesoftimersistheProgrammableIntervalTimer,orPITforshort.APITjustcountsdownfromsomevaluetozero.Onceitreacheszero,itsendsaninterrupttotheprocessorindicatingthatithasfinishedcounting.Thisisusefulfordevicessuchasthermostats,whichperiodicallytestthetemperaturearoundthemtoseeiftheyneedtoturntheairconditioneron,theheateron,etc.

TimeProcessingUnitorTPUforshort.Isessentiallyjustanothertimer,butmoresophisticated.Inadditiontocountingdown,theTPUcandetectinputevents,generateoutputevents,andotherusefuloperations.

DedicatedPulseWidthModulation（PWM）blockmakesitpossiblefortheCPUtocontrolpowerconverters,resistiveloads,motors,etc.,withoutusinglotsofCPUresourcesintighttimerloops.

UniversalAsynchronousReceiver/Transmitter（UART）blockmakesitpossibletoreceiveandtransmitdataoveraseriallinewithverylittleloadontheCPU.

ForthosewantingethemetonecanuseanexternalchiplikeCrystalSemiconductorCS8900A,RealtekRTL8019,orMicrochipENC28J60.Allofthemalloweasyinterfacingwithlowpincount.

（2）Externaloscillatorandcrystal

Externalcrystalisasimpleandstraightforwardconnectionwiththechipandtheloadcapacitanceofthecrystalpart,checkthedatasheet,usually,however,theoscillatorfrequencyandthechipcanbedirectlyconnectedtopins,withoutdecouplingcapacitor.Tendtorequireahighfrequencyoscillatorcapacitor,ifyouareveryluckytohaveaccurateTTLorCMOSleveloscillator,itjustneedstobeconnectedtoXINpin,closeOscillatorusingOSCOff,XOUTcanalsobeavacantground.

Digitallycontrolledoscillatorbyconnectingaresistorintheexternaloscillator,I'mnotsure,butyouwill,sothatwecaninthisconfigurationusinganexternaldigitalvoltmetertestexecutionoscillationiscorrect,thiswillbeverycheap,simpleandmorereliabletouseon-chiposcillatorsufficientlyaccurate.I'msureinthefuturethere