Renesas SH7781 - Manual (Page 1280)

24. Multimedia Card Interface (MMCIF)
Rev.1.00 Jan. 10, 2008 Page 1250 of 1658
REJ09B0261-0100
24.6.2 Operation in Write Sequence
To transfer data to FIFO with the DMAC, set MMCIF (DMACR) after setting the DMAC. Then,
start transfer to the card after a FIFO ready interrupt. Figure 24.26 to 24.28 shows the operational
flow for a write sequence.
• Clear FIFO.
• Transmit write command.
• Make settings in DMACR, and set write data to FIFO.
• Check whether data exceeding the DMACR setting condition is written to FIFO by a FIFO
ready interrupt (FRDYI) or DMAC has transferred all data to FIFO. Then set 1 to the
DATAEN bit in OPCR to start write-data transmission.
In a write to the card by stream transfer, the MMCIF continues data transfer to the card even
after a FIFO empty interrupt is detected. Therefore, complete the write sequence after at least
24 card clock cycles.
• Confirm that the DMAC transfer is completed and be sure to clear the DMAEN bit in
DMACR to 0.
• Set the CMDOFF bit to 1 if a CRC error (CRCERI) or a data timeout error (DTERI) occurs in
the command response reception.
• Set the CMDOFF bit to 1, clear FIFO, and clear DMACR to H'00 if a CRC error (CRCERI) or
a data timeout error (DTERI) occurs in the write data transmission.
When using DMA, an inter-block interrupt can be processed by hardware in pre-defined multiple
block transfer by setting the AUTO bit in DMACR to 1. Figure 24.29 shows the operational flow
for a pre-defined multiple block write sequence using auto-mode.
• Clear FIFO.
• Set the block number to TBNCR.
• Set the CMDSTART bit in CMDSTRT to 1 and begin command transmission.
• Command response is received from the card.
• A command timeout error (CTERI) is detected if a command response is not received from the
card.
• Set DMACR and write data in FIFO.
• Confirm that the DMA transfer has been completed and clear the DMAEN bit in DMACR to
0.
• Detect the end of the command sequence by poling the BUSY flag in CSTR or through the
pre-defined multiple block transfer end flag (BTI).