Renesas SH7781 - Manual (Page 1270)

24. Multimedia Card Interface (MMCIF)
Rev.1.00 Jan. 10, 2008 Page 1240 of 1658
REJ09B0261-0100
24.6 Operations when Using DMA
24.6.1 Operation in Read Sequence
In order to transfer data in FIFO with the DMAC, set MMCIF (DMACR) after setting the
DMAC*. Transmit the read command after setting DMACR.
Figure 24.22 to 24.24 shows the operational flow for a read sequence.
• Clear FIFO and make settings in DMACR.
• Read command transmission is started.
• Command response is received from the card.
• Read data is received from the card.
• After the read sequence, data remains in FIFO. If necessary, write 100 to SET[2:0] in DMACR
to read all data from FIFO.
• Confirm that the DMAC transfer is completed and set the DMAEN bit in DMACR to 0.
• Set the CMDOFF bit to 1 and clear DMACR to H'00 if a CRC error (CRCERI) or a command
timeout error (CTERI) occurs in the command response reception.
• Set the CMDOFF bit to 1, clear DMACR to H'00, and clear FIFO if a CRC error (CRCERI) or
a data timeout error (DTERI) occurs in the read data reception.
When using DMA, next block read is resumed automatically when the AUTO bit in DMACR is
set to 1 and normal read is detected after the block transfer end of a pre-defined multiple block
transfer. Figure 24.25 shows the operational flow for a pre-defined multiple block read using auto-
mode.
• Clear FIFO.
• Set the block number to (TBNCR).
• Set DMACR.
• Read command transmission is started.
• Command response is received from the card.
• Read data is received from the card.
• Detect the command timeout error (CTERI) if a command response is not received from the
card.
• The end of the command sequence is detected by poling the BUSY flag in CSTR or through
the pre-defined multiple block transfer end flag (BTI).