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2.10InterruptSupport
2.10.1InterruptEventsandRequests
2.10.2InterruptMultiplexing
PeripheralArchitecture
TheMMC/SDcontrollergeneratestheinterruptrequestsdescribedinTable4.Whenaninterruptevent
occurs,itsflagbitissetintheMMCstatusregister0(MMCST0).Iftheenablebitscorrespondingtoeach
flagaresetintheMMCinterruptmaskregister(MMCIM),aninterruptrequestgenerates.Allsuch
requestsaremultiplexedtoasingleMMC/SDinterruptrequestfromtheMMC/SDperipheraltotheARM
CPU.
TheMMC/SDinterruptsarepartofthemaskableARMinterrupts.TheARMinterrupt26(INT26)is
associatedwithMMCfunctionsandtheARMinterrupt27(INT27)isassociatedwithSDfunctions.The
interruptserviceroutine(ISR)fortheMMC/SDinterruptcandeterminetheeventthatcausedtheinterrupt
bycheckingthebitsinMMCST0.WhenMMCST0isread,allregisterbitsautomaticallyclear.Duringa
middleofdatatransfer,theDXRDYandDRRDYbitsaresetduringevery128-byteor256-bytetransfer,
dependingonthetheMMCFIFOcontrolregister(MMCFIFOCTL)setting.Performingawriteandareadin
responsetotheinterruptgeneratedbytheFIFOautomaticallyclearsthecorrespondinginterruptbit/flag.
Note:Youmustbeawarethatanemulationreadofthestatusregisterclearstheinterruptstatus
flags.Toavoidinadvertentlyclearingtheflag,becarefulwhilemonitoringMMCST0via
thedebugger.
TheinterruptsfromtheMMC/SDperipheraltotheARMCPUarenotmultiplexedwithanyotherinterrupt
source.
Table4.DescriptionofMMC/SDInterruptRequests
Interrupt
RequestInterruptEvent
TRNDNEINTForreadoperations:TheMMC/SDcontrollerhasreceivedthelastbyteofdata(beforeCRCcheck).
Forwriteoperations:TheMMC/SDcontrollerhastransferredthelastwordofdatatotheoutputshiftregister.
DATEDINTAnedgewasdetectedontheDAT3pin.
DRRDYINTMMCDRRisreadytoberead(datainFIFOisabovethreshold).
DXRDYINTMMCDXRisreadytotransmitnewdata(datainFIFOislessthanthreshold).
CRCRSINTACRCerrorwasdetectedinaresponsefromthememorycard.
CRCRDINTACRCerrorwasdetectedinthedatareadfromthememorycard.
CRCWRINTACRCerrorwasdetectedinthedatawrittentothememorycard.
TOUTRSINTAtime-outoccurredwhiletheMMCcontrollerwaswaitingforaresponsetoacommand.
TOUTRDINTAtime-outoccurredwhiletheMMCcontrollerwaswaitingforthedatafromthememorycard.
RSPDNEINTForacommandthatrequiresaresponse:TheMMCcontrollerhasreceivedtheresponsewithoutaCRCerror.
Foracommandthatdoesnotrequirearesponse:TheMMCcontrollerhasfinishedsendingthecommand.
BSYDNEINTThememorycardstopsorisnolongersendingabusysignalwhentheMMCcontrollerisexpectingabusysignal.
DATDNEINTForreadoperations:TheMMCcontrollerhasreceiveddatawithoutaCRCerror.
Forwriteoperations:TheMMCcontrollerhasfinishedsendingdata.
SPRUE30B–September2006MultimediaCard(MMC)/SecureDigital(SD)CardController27
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