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1、中文2330字THEMICROPROCESSORSYSTEMAmicroprocessorsystemcanbedescribedatanumberofdifferentlevelsofcomplexity.Theleastcomplexfromisthatofasimpleblockdiagramdescribingtheinterconnectionandflowofinformationfunctionalblocksandwillbeusedtoexaminetheoperationofamicroprocessorsystem.Allmicroprocessor
2、systemscontainacentralprocessingunit(CPU),programanddatamemoryandinput(I/O)devices.Fig.4-4showablockdiagramofatypicalembeddedmicroprocessorsysteminwhicheachblockcorrespondsroughlytotheindividualintegratedcircuit(chip)usedinthesystem.Thememorysectioncontainsbothnon-volatilereadonlymemory(R
3、OM)asprogrammemoryandvolatilerandomaccessmemory(RAM)asread/writedatamemory.Foreachtypeofmemorythereareanumberofdifferenttypesofdevices,suchaserasableROMsandstaticordynamicRAMs,eachofwhichischosenforanapplicationbasedonitscostandfunction.FourdifferentI/OfunctionsareshowninFig.4-4.Ananalogu
4、einputchanneltothemicroprocessorsystemisprovidedbytheanaloguetodigital(A/D)converterandmaybeusedtoconnectadevicesuchasananaloguetodigital(A/D)converterandmaybeusedtoconnectadevicesuchasananaloguesensor.Ananalogueoutputchannelisprovidedbythedigitaltoanalogue(D/A)converterandcouldbeusedtoco
5、ntrolanoutputtransducersuchasanelectricmotor,TheparallelI/Odeviceprovidesanumberofindividuallines.Inoutputmodethesecanbeprogrammedtoprovidelogiclevels1or0toactivatebinary(on/off)devicessuchaslamps.Ininputmodeitallowsthemicroprocessortoreadthestateofswitchesandotherbinarydevices.TheserialI
6、/Odeviceisusedtoprovidecommunicationswithothermicroprocessorsystemsorwithanoperatorconsoleusedtoconfigurethesystemforvariousoperationalmodes.Thelevelandpowerspecificationsoftheinterfacingsignalsofthemicroprocessorsystemarefrequentlyincompatiblewiththesignalspecificationsofthedeviceswhicha
7、retobeinterfacedtoit.Forexample,theoutputvoltageofaD/Aconvertermaytypicallybeintherange0-5voltsandbecapableofsupplyingonlyafewmilliamperesofcurrent,Fig.4-4Blockdiagramofatypicalembeddedmicroprocessorsystemwhiletheelectricmotormayrequireacontrolvoltagerangeofplusandm
