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1、外文资料原文TransmittingandreceivingserialdataTheUniversalAsynchronousReceiver/Transmitter(UART)controlleristhekeycomponentoftheserialcommunicationssubsystemofacomputer.TheUARTtakesbytesofdataandtransmitstheindividualbitsinasequentialfashion.Atthedestination,asecondUARTre-a
2、ssemblesthebitsintocompletebytes.Serialtransmissionofdigitalinformation(bits)throughasinglewireorothermediumismuchmorecosteffectivethanparalleltransmissionthroughmultiplewires.AUARTisusedtoconvertthetransmittedinformationbetweenitssequentialandparallelformateachendoft
3、helink・EachUARTcontainsashiftregisterwhichisthefundamentalmethodofconversionbetweenserialandparallelforms.TheUARTusuallydoesnotdirectlygenerateorreceivetheexternalsignalsusedbetweendifferentitemsofequipment.Typically,separateinterfacedevicesareusedtoconvertthelogiclev
4、elsignalsoftheUARTtoandfromtheexternalsignalinglevels.Externalsignalsmaybeofmanydifferentforms.ExamplesofstandardsforvoltagesignalingareRS-232,RS-422andRS-485fromtheEIA.Historically,thepresenceorabsenceofcurrent(incurrentloops)wasusedintelegraphcircuits.Somesignalings
5、chemesdonotuseelectricalwires.Examplesofsucharcopticalfiber,IrDA(infrared),and(wireless)BluetoothinitsSerialPortProfile(SPP).Somesignalingschemesusemodulationofacarriersignal(withorwithoutwires).Examplesarcmodulationofaudiosignalswithphonelinemodems,RFmodulationwithda
6、taradios,andtheDC-LINforpowerlinecommunication.Communicationmaybenfullduplex"(bothsendandreceiveatthesametime)orHhalfduplex11(devicestaketurnstransmittingandreceiving).Asof2008,UARTsarecommonlyusedwithRS-232forembeddedsystemscommunications-Itisusefultocommunicatebetwe
7、enmicrocontrollersandalsowithPCs.ManychipsprovideUARTfunctionalityinsilicon,andlow-costchipsexisttoconvertlogiclevelsignals(suchasTTLvoltages)toRS-232levelsignals(forexample,Maxim'sMAX232)・错误！超链接引用无效。AsynchronousreceiveandtransmitInasynchronoustransmitting,teletype-st
8、yleUARTssenda"start”bit,fivetoeightdatabits,least-significant-bitfirst,anoptional"parity”bit,andthenone,oneandahalf,ortwo"st
