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전자부품 데이터시트 검색엔진 |
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전자부품 데이터시트 검색엔진 |
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HT45F75 데이터시트(PDF) 139 Page - Holtek Semiconductor Inc |
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HT45F75 데이터시트(HTML) 139 Page - Holtek Semiconductor Inc |
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139 / 190 page  Rev. 1.10 138 De�e��e� 1�� �01� Rev. 1.10 139 De�e��e� 1�� �01� HT45F75 Body Fat Scale Flash MCU HT45F75 Body Fat Scale Flash MCU Duringadatatransmission,awriteinstructiontotheTXRregisterwillplacethedataintotheTXR register,whichwillbecopiedtotheshiftregisterattheendofthepresenttransmission.Whenthere isnodatatransmissioninprogress,awriteinstructiontotheTXRregisterwillplacethedatadirectly intotheshiftregister,resultinginthecommencementofdatatransmission,andtheTXIFbitbeing immediatelyset.Whenaframetransmissioniscomplete,whichhappensafterstopbitsaresent orafterthebreakframe,theTIDLEbitwillbeset.TocleartheTIDLEbitthefollowingsoftware sequenceisused: 1.AUSRregisteraccess 2.ATXRregisterwriteexecution NotethatboththeTXIFandTIDLEbitsareclearedbythesamesoftwaresequence. Transmit Break IftheTXBRKbitissetthenbreakcharacterswillbesentonthenexttransmission.Breakcharacter transmissionconsistsofastartbit,followedby13×N‘0’bitsandstopbits,whereN=1,2,etc.Ifa breakcharacteristobetransmittedthentheTXBRKbitmustbefirstsetbytheapplicationprogram, thenclearedtogeneratethestopbits.Transmittingabreakcharacterwillnotgenerateatransmit interrupt.Notethatabreakconditionlengthisatleast13bitslong.IftheTXBRKbitiscontinually keptatalogichighlevelthenthetransmittercircuitrywilltransmitcontinuousbreakcharacters. AftertheapplicationprogramhasclearedtheTXBRKbit,thetransmitterwillfinishtransmittingthe lastbreakcharacterandsubsequentlysendoutoneortwostopbits.Theautomaticlogichighsatthe endofthelastbreakcharacterwillensurethatthestartbitofthenextframeisrecognized. UART Receiver TheUARTiscapableofreceivingwordlengthsofeither8or9bits.IftheBNObitisset,theword lengthwillbesetto9bitswiththeMSBbeingstoredintheRX8bitoftheUCR1register.Atthe receivercoreliestheReceiveSerialShiftRegister,commonlyknownastheRSR.Thedatawhich isreceivedontheRXexternalinputpin,issenttothedatarecoveryblock.Thedatarecoveryblock operatingspeedis16timesthatofthebaudrate,whilethemainreceiveserialshifteroperatesatthe baudrate.AftertheRXpinissampledforthestopbit,thereceiveddatainRSRistransferredtothe receivedataregister,iftheregisterisempty.ThedatawhichisreceivedontheexternalRXinputpin issampledthreetimesbyamajoritydetectcircuittodeterminethelogiclevelthathasbeenplaced ontotheRXpin.ItshouldbenotedthattheRSRregister,unlikemanyotherregisters,isnotdirectly mappedintotheDataMemoryareaandassuchisnotavailabletotheapplicationprogramfordirect read/writeoperations. Receiving Data WhentheUARTreceiverisreceivingdata,thedataisseriallyshiftedinontheexternalRXinput pin,LSBfirst.Inthereadmode,theRXRregisterformsabufferbetweentheinternalbusandthe receivershiftregister.TheRXRregisterisatwobytedeepFIFOdatabuffer,wheretwobytescan beheldintheFIFOwhileathirdbytecancontinuetobereceived.Notethattheapplicationprogram mustensurethatthedataisreadfromRXRbeforethethirdbytehasbeencompletelyshifted in,otherwisethisthirdbytewillbediscardedandanoverrunerrorOERRwillbesubsequently indicated.Thestepstoinitiateadatatransfercanbesummarizedasfollows: • MakethecorrectselectionofBNO,PRT,PRENandSTOPSbitstodefinethewordlength,parity typeandnumberofstopbits. • SetuptheBRGregistertoselectthedesiredbaudrate. • SettheRXENbittoensurethattheRXpinisusedasaUARTreceiverpin. Atthispointthereceiverwillbeenabledwhichwillbegintolookforastartbit. |
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