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1、Ch8???Serial?Port?Communicate?TechnologylKeywords:串行口(SerialPort)并行口(ParallelPort)通信(Communication)字符幀(Characterframe)波特率(BaudRate)異步通信(AsynchronousCommunication)同步通信(SynchronousCommunication)通用異步收發(fā)器(UART,UniversalAsynchronousReceiverTransmitter)通用同步收發(fā)器(US
2、RT,UniversalSynchronousReceiver/Transmitter)全雙工(FD/FDX,F(xiàn)ullDuplex)半雙工(Semiduplex)單工(SPX,Simplex)lIntroduction:????Each8031microcomputercontainsahighspeedfullduplex(meansyoucansimultaneouslyusethesameportforbothtransmittingandreceivingpurposes)serialportwhi
3、chissoftwareconfigurablein4basicmodes:8bitUART;9bitUART;InterprocessorCommunicationslinkorasshiftregisterI/Oexpander.??????????Forthestandardserialcommunicationfacility,8031canbeprogrammedforUARToperationsandcanbeconnectedwithregularpersonalcomputers,telet
4、ypewriters,modematdataratesbetween122baudsand31kilobauds.Gettingthisfacilityismadeverysimpleusingsimpleroutineswithoptiontoselectevenoroddparity.YoucanalsoestablishakindofInterprocessorcommunicationfacilityamongmanymicrocomputersinadistributedenvironmentwi
5、thautomaticrecognitionofaddress/data.????????????????????????????????Apartfromallabove,youcanalsogetsuperfastI/OlinesusinglowcostsimpleTTLorCMOSshiftregisters.?????Communicationwithexternaldevicesoverdistancesofmorethanafewfeetisoftendoneinaserialmanner–on
6、ebitatatimeoveroneortwolines(onelineforreceivinginformationandoneforsending).The8051familyofmicrocontrollerstypicallyincludeaUniversalAsynchronousReceiverTransmitter(UART)forthispurpose.ThisisthesametypeofdeviceusedtoimplementtheCOMportsofaPC.Althoughitisp
7、ossibletousesimplesoftwarepollingroutinestoserviceaUART,itwastesCPUtimeandpreventstheCPUfromperformingothertasks,sointerruptsaremorecommonlyused.Inthislab,youwilldesignaprogramtosendandreceiveserialdatausinginterrupts.AUARTdevicedrivercanbedifficulttodebug
8、usingstandardsoftware-simulationtools.Insuchcases,itiscommontodevelopmodelsthatsimulateexternalhardwareandallowyoutoseehowyourhardware-softwaredesignwillinteractwiththishardware.Amodelofanexternalserialdevice