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HT66F4530 数据表(PDF) 159 Page - Holtek Semiconductor Inc |
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HT66F4530 数据表(HTML) 159 Page - Holtek Semiconductor Inc |
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159 / 224 page ![]() Rev. 1.00 158 De�e��e� �1� �01� Rev. 1.00 159 De�e��e� �1� �01� HT66F4530/HT66F4540/HT66F4550 A/D Flash MCU with Dual Operational Amplifiers HT66F4530/HT66F4540/HT66F4550 A/D Flash MCU with Dual Operational Amplifiers UART Transmitter Datawordlengthsofeither8or9bitscanbeselectedbyprogrammingtheBNObitintheUCR1 register.WhenBNObitisset,thewordlengthwillbesetto9bits.Inthiscasethe9thbit,which istheMSB,needstobestoredintheTX8bitintheUCR1register.Atthetransmittercorelies theTransmitterShiftRegister,morecommonlyknownastheTSR,whosedataisobtainedfrom thetransmitdataregister,whichisknownastheTXR_RXRregister.Thedatatobetransmitted isloadedintothisTXR_RXRregisterbytheapplicationprogram.TheTSRregisterisnotwritten towithnewdatauntilthestopbitfromtheprevioustransmissionhasbeensentout.Assoonas thisstopbithasbeentransmitted,theTSRcanthenbeloadedwithnewdatafromtheTXR_RXR register,ifitisavailable.ItshouldbenotedthattheTSRregister,unlikemanyotherregisters,isnot directlymappedintotheDataMemoryareaandassuchisnotavailabletotheapplicationprogram fordirectread/writeoperations.Anactualtransmissionofdatawillnormallybeenabledwhenthe TXENbitisset,butthedatawillnotbetransmitteduntiltheTXR_RXRregisterhasbeenloaded withdataandthebaudrategeneratorhasdefinedashiftclocksource.However,thetransmission canalsobeinitiatedbyfirstloadingdataintotheTXR_RXRregister,afterwhichtheTXENbitcan beset.Whenatransmissionofdatabegins,theTSRisnormallyempty,inwhichcaseatransferto theTXR_RXRregisterwillresultinanimmediatetransfertotheTSR.Ifduringatransmissionthe TXENbitiscleared,thetransmissionwillimmediatelyceaseandthetransmitterwillbereset.The TXoutputpincanthenbeconfiguredastheI/Oorotherpin-sharedfunctionbyconfiguringthe correspondingpin-sharedcontrolbits. Transmitting Data WhentheUARTistransmittingdata,thedataisshiftedontheTXpinfromtheshiftregister,with theleastsignificantbitfirst.Inthetransmitmode,theTXR_RXRregisterformsabufferbetween theinternalbusandthetransmittershiftregister.Itshouldbenotedthatif9-bitdataformathasbeen selected,thentheMSBwillbetakenfromtheTX8bitintheUCR1register.Thestepstoinitiatea datatransfercanbesummarizedasfollows: • MakethecorrectselectionoftheBNO,PRT,PRENandSTOPSbitstodefinetherequiredword length,paritytypeandnumberofstopbits. • SetuptheBRGregistertoselectthedesiredbaudrate. • SettheTXENbittoensurethattheTXpinisusedasaUARTtransmitterpin. • AccesstheUSRregisterandwritethedatathatistobetransmittedintotheTXR_RXRregister. NotethatthisstepwillcleartheTXIFbit. Thissequenceofeventscannowberepeatedtosendadditionaldata. ItshouldbenotedthatwhenTXIF=0,datawillbeinhibitedfrombeingwrittentotheTXR_RXR register.ClearingtheTXIFflagisalwaysachievedusingthefollowingsoftwaresequence: 1.AUSRregisteraccess 2.ATXR_RXRregisterwriteexecution Theread-onlyTXIFflagissetbytheUARThardwareandifsetindicatesthattheTXR_RXR registerisemptyandthatotherdatacannowbewrittenintotheTXR_RXRregisterwithout overwritingthepreviousdata.IftheTEIEbitissetthentheTXIFflagwillgenerateaninterrupt. |
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