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1、Ch6???The?Expanded?System?of?Single?Chip?MicrocomputerlKeywords：靜態(tài)RAM（SRAM，StaticRandomAccessMemory）動態(tài)RAM（DRAM，DynamicRandomAccessMemory）快擦寫型存儲器（FlashMemory）只讀存儲器（ROM，Read-onlyMemory）隨機存取存儲器（RAM，RandomAccessMemory）lIntroduction：????The8031'sDataMemorymaynotbe
2、usedforprogramstorage.Soitmeansyoucan'texecuteinstructionsoutofthisDataMemory.???But,thereisawaytohaveasingleblockofoffchipmemoryactingasbothProgramandDataMemory.Bygatingtogetherbothmemoryreadcontrols(RDandPSEN)usinganANDgate,acommonmemoryreadcontrolsignalcan
3、begenerated.?Inthisarrangement,bothmemoryspacesaretiedtogetherandtotalaccessiblememoryisreducedfrom128Kbytesto64Kbytes.?????The8031canreadandwriteintothiscommonmemoryblockanditcanbeusedasProgramandDataMemory.??Youcanusethisarrangementduringprogramdevelopmenta
4、nddebuggingphase.WithouttakingMicrocontrolleroffthesockettoprogramitsinternalROM(EPROM/FlashROM),youcanusethiscommonmemoryforfrequentprogramstorageandcodemodifications.????????Thetipicalexpandedchipof8031is8155and8255.8155isa2048-bitstaticMOSRAMwithi/oportsan
5、dtimer.????8255provides24I/Opinswhichmaybeindividuallyprogrammedin2groupsof12andusedin3majormodesofoperation.InMODE0,eachgroupof12I/Opinsmaybeprogrammedinsetsof4and8tobeinputsoroutputs.InMODE1,eachgroupmaybeprogrammedtohave8linesofinputoroutput.3oftheremainin
6、g4pinsareusedforhandshakingandinterruptcontrolsignals.MODE2isastrobedbi-directionalbusconfiguration.8255isaprogrammableperipheralinterfacedevicedesignedforuseinIntelmicrocomputersystems.ItsfunctionisthatofageneralpurposeI/Ocomponenttointerfaceperipheralequipm
7、enttothemicrocomputersystembus.Thefunctionalconfigurationofthe8255isprogrammedbythesystemsoftwaresothatnormallynoexternallogicisnecessarytointerfaceperipheraldevicesorstructures.????This3-statebidirectional8-bitbufferisusedtointerfacethe8255tothesystemdatabus
8、.DataistransmittedorreceivedbythebufferuponexecutionofinputoroutputinstructionsbytheCPU.Controlwordsandstatusinformationarealsotransferredthroughthedatabusbuffer.????Thefunctionofthisbloc
