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DetailedDescription
autoflowcontrol(seefigure2)
TL16C2550
SLWS161–JUNE2005
deviceinformation(持续)
terminalfunctions(持续)
终端
i/odescription
namepfbno.fnno.rhbno.
ringindicator(activelow).theseinputsareassociatedwithindividual
uartchannelsaandb.alogiclowonthesepinsindicatesthemodem
hasreceivedaringingsignalfromthetelephoneline.alowtohigh
ria,rib41,2143,26–i
transitionontheseinputpinsgeneratesamodemstatusinterrupt,如果
使能.thestateoftheseinputsisreflectedinthemodemstatusregister
(msr)
requesttosend(activelow).theseoutputsareassociatedwithindividual
uartchannelsaandb.alowonthertspinindicatesthetransmitterhas
datareadyandwaitingtosend.writinga1inthemodemcontrolregister
rtsa,
33,2236,2723,15o(mcrbit1)setsthesepinstolow,indicatingdataisavailable.afterareset,
RTSB
thesepinsaresettohigh.thesepinsonlyaffectsthetransmitandreceive
operationwhenautoRTSfunctionisenabledthroughtheenhancedfeature
寄存器(efr)bit6,forhardwareflowcontroloperation.
receivedatainput.theseinputsareassociatedwithindividualserial
channeldatatothe2550.duringthelocalloopbackmode,theserxinput
rxa,rxb5,411,104,3i
pinsaredisabledandTXdataisinternallyconnectedtotheUARTRXinput
内部.
receiveready(activelow).rxrdyaandbgoeslowwhenthetrigger
rxrdya,
31,1834,23–olevelhasbeenreachedoratimeoutinterruptoccurs.theygohighwhen
RXRDYB
therxfifoisemptyorthereisanerrorinrxfifo.
transmitdata.theseoutputsareassociatedwithindividualserialtransmit
txa,txb7,813,145,6ochanneldatafromthe2550.duringthelocalloopbackmode,thetxinput
pinisdisabledandtxdataisinternallyconnectedtotheuartrxinput.
transmitready(activelow).txrdyaandbgolowwhenthereareatleast
txrdya,
43,611,12–oatriggerlevelnumbersofspacesavailable.theygohighwhenthetx
TXRDYB
bufferisfull.
V
CC
424426ipowersupplyinputs.
crystalorexternalclockinput.xtal1functionsasacrystalinputorasan
externalclockinput.acrystalcanbeconnectedbetweenxtal1and
XTAL1131810I
xtal2toformaninternaloscillatorcircuit(seefigure10).alternatively,一个
externalclockcanbeconnectedtoxtal1toprovidecustomdatarates.
outputofthecrystaloscillatororbufferedclock.seealsoxtal1.xtal2is
XTAL2141911O
usedasacrystaloscillatoroutputorbufferedaclockoutput.
autoflowcontroliscomprisedofauto-ctsandauto-rts.withauto-cts,thectsinputmustbeactivebefore
thetransmitterfifocanemitdata.withauto-rts,rtsbecomesactivewhenthereceiverneedsmoredataand
notifiesthesendingserialdevice.whenrtsisconnectedtocts,datatransmissiondoesnotoccurunlessthe
receiverfifohasspaceforthedata;因此,overrunerrorsareeliminatedusingace1andace2froma
tlc16c2550withtheautoflowcontrolenabled.ifnot,overrunerrorsoccurwhenthetransmitdatarateexceeds
thereceiverfiforeadlatency.
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