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2.9.7.8DeterminingWhenLastDatahasBeenWrittentoCard(SanDiskSDcards)
2.9.7.9CheckingForaDataTransmitEmptyCondition
2.9.7.10CheckingforaDataReceiveFullCondition
2.9.7.11CheckingtheStatusoftheSD_CLKPin
2.9.7.12CheckingtheRemainingBlockCountDuringaMultiple-BlockTransfer
PeripheralArchitecture
SomeSanDiskbrandSD™cardsexhibitabehaviorthatrequiresamultiple-blockwritecommandto
terminatewithaSTOP(CMD12)commandbeforethedatawritesequencecompletes.Toenablesupport
ofthisfunction,thetransferdoneinterrupt(TRNDNE)isprovided.SettheETRNDNEbitinMMCIMto
enabletheTRNDNEinterrupt.Thisinterruptisissuedwhenthelastbyteofdata(asdefinedby
MMCNBLKandMMCBLEN)istransferredfromtheFIFOtotheoutputshiftregister.TheCPUshould
respondtothisinterruptbysendingaSTOPcommandtothecard.ThisinterruptdiffersfromDATDNEby
timing.DATDNEdoesnotoccuruntilaftertheCRCandmemoryprogrammingarecomplete.
Duringtransmission,adatavalueispassedfromtheMMCdatatransmitregister(MMCDXR)tothedata
transmitshiftregister.Thedataisthenpassedfromtheshiftregistertothememorycardonebitatatime.
TheDXEMPbitinMMCST1indicateswhentheshiftregisterisempty.
Typically,theDXEMPbitisnotusedtocontroldatatransfers;rather,itischeckedduringrecoveryfroman
errorcondition.ThereisnointerruptassociatedwiththeDXEMPbit.
Duringreception,thedatareceiveshiftregisteracceptsadatavalueonebitatatime.Theentirevalueis
thenpassedfromtheshiftregistertotheMMCdatareceiveregister(MMCDRR).TheDRFULbitin
MMCST1indicatesthatwhentheshiftregisterisfullnonewbitscanbeshiftedinfromthememorycard.
TheDRFULbitisnottypicallyusedtocontroldatatransfers;rather,itischeckedduringrecoveryfroman
errorcondition.ThereisnointerruptassociatedwiththeDRFULbit.
ReadtheCLKSTPbitinMMCST1todeterminewhetherthememoryclockhasbeenstoppedonthe
SD_CLKpin.
Duringatransferofmultipledatablocks,theMMCnumberofblockscounterregister(MMCNBLC)
indicateshowmanyblocksareremainingtobetransferred.TheMMCNBLCisaread-onlyregister.
MultimediaCard(MMC)/SecureDigital(SD)CardController 26SPRUE30B–September2006
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