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ARG HIGH
RCA ADDRESS HIGH
STATUS 0
NEXT DATA BYTE
DATA TX
MMC controller
register content
MMC controller
register
RCA ADDRESS LOW
ARG LOW
SEL/DESEL. CARD
COMMAND
Select one card with relative
card address (RCA) while
de−selecting the other cards.
SET_BLOCKLEN
BLK ADDRESS LOW
BLK ADDRESS HIGH
COMMAND
ARG LOW
ARG HIGH
READ_SINGLE_BLOCK
COMMAND
Load starting block address
into the high and low argument
registers. Load block
length register. Start the
operation by loading a
Is CRCWR = 1?
Is DXRDY = 1?
READ_SINGLE_BLOCK
command into the command
register.
Check CRCWR bit for any write
CRC errors.
Check DXRDY to see if a new
byte can be put in MMCDXR
register.
STOP_TRANSMISSION
COMMAND
Terminate the multiple−block
write operation.
3.5MMC/SDModeSingle-BlockReadOperationUsingEDMA
ProceduresforCommonOperations
Figure15.MMC/SDModeSingle-BlockReadOperation
Toperformasingle-blockread,thesameblocklengthneedstobesetinboththeMMC/SDcontrollerand
thecard.Theprocedureforthisoperationis:
1.Writethecard’srelativeaddresstotheMMCargumentregisters(MMCARGHandMMCARGL).Load
thehighpartoftheaddresstoMMCARGHandthelowpartoftheaddresstoMMCARGL.
2.ReadcardCSDtodeterminethecard'smaximumblocklength.
3.UsetheMMCcommandregister(MMCCMD)tosendtheSET_BLOCKLENcommand(iftheblock
lengthisdifferentthanthelengthusedinthepreviousoperation).Theblocklengthmustbeamultiple
of512bytesandlessthenthemaximumblocklengthspecifiedintheCSD.
4.ResettheFIFO(FIFORSTbitinMMCFIFOCTL).
5.SettheFIFOdirectiontoreceive(FIFODIRbitinMMCFIFOCTL).
6.Settheaccesswidth(ACCWDbitsinMMCFIFOCTL).
7.SettheFIFOthreshold(FIFOLEVbitinMMCFIFOCTL).
8.SetupDMA(DMAsizeneedstobegreaterthanorequaltoFIFOLEVsetting).
9.UseMMCCMDtosendtheREAD_BLOCKcommandtothecard.
10.WaitforDMAsequencetocomplete.
11.UsetheMMCstatusregister0(MMCST0)tocheckforerrors.
SPRUE30B–September2006MultimediaCard(MMC)/SecureDigital(SD)CardController35
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