Texas Instruments TMS320DM644x Manuel D’Utilisation

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_MULT_BLOCK

COMMAND

Load starting block address
into the high and low argument
registers. Load block
length register with the block
length value. Start the operation by

Is CRCRD = 1?
Is DRRDY = 1?

loading a READ_MULTIPLE_BLOCK
command into the command
register.

Check TOUTRD bit to verify
that the read operation has not
timed−out. Check CRCRD bit for
any read CRC errors. Check DRRDY
to see if a new byte is in the data

STOP_TRANSMISSION

COMMAND

Terminate the multiple−block
read operation.

Is TOUTRD = 1?

receive register.

To perform a multiple-block read, the same block length must be set in both the MMC/SD controller and
the card.

The procedure for this operation is as follows:

1. Write the card’s relative address to the MMC argument registers (MMCARGH and MMCARGL). Load

the high part of the address to MMCARGH and the low part of the address to MMCARGL.

2. Read card CSD to determine the card's maximum block length.
3. Use the MMC command register (MMCCMD) to send the SET_BLOCKLEN command (if the block

length is different than the length used in the previous operation). The block length must be a multiple
of 512 bytes and less then the maximum block length specified in the CSD.

4. Reset the FIFO (FIFORST bit in MMCFIFOCTL).
5. Set the FIFO direction to receive (FIFODIR bit in MMCFIFOCTL).
6. Set the FIFO threshold (FIFOLEV bit in MMCFIFOCTL).
7. Set the access width (ACCWD bits in MMCFIFOCTL).
8. Set up DMA (DMA size needs to be greater than or equal to FIFOLEV setting).
9. Use MMCCMD to send the READ_MULTI_BLOCK command to the card.
10. Wait for DMA sequence to complete.
11. Use the MMC status register 0 (MMCST0) to check for errors.
12. Use MMCCMD to send the STOP_TRANSMISSION command.

SPRUE30B – September 2006

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