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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
