Intel PXA255 - Manual (Page 518)

15-16 Intel® PXA255 Processor Developer’s Manual
MultiMediaCard Controller
In a stream data write, the following parameters must be specified:
• The data transfer is a write.
• The data transfer is in stream mode
• The block length, if the block length is different from the previous block data transfer or this is
the first time that the parameter is being specified.
• The number of blocks to be transferred as 0xffff.
15.3.2.4 Stream Data READ
The stream data read looks like the single block read except a stop transmission command must be
sent after the data transfer.
After turning the clock on to start the command sequence, the software must start the process of
reading the MMC_RXFIFO as described in
Section 15.3.2.2 .
When it uses the DMA, the software must also configure the DMA to send an interrupt after all
data has been read. After the DMA interrupt or the program has read all of the data, the software
must send the stop transmission command. The MCC_STAT[DATA_TRAN_DONE] bit is not set
until after software sends the stop transmission command.
In a stream data read, the following parameters must be specified:
• The data transfer is a read.
• The data transfer is in stream mode.
• The block length, if the block length is different from the previous block data transfer or this is
the first time that the parameter is being specified.
• The number of blocks to be transferred as 0xffff.
• The receive data time-out period.
15.3.3 Busy Sequence
The MMC controller expects a busy signal automatically from the card after every block of data for
single and multiple block write operations. It will also expect a busy at the end of a command every
time that the software specifies that a busy signal is expected (i.e. a busy signal is expected after the
commands for stop transmission, card select, erase, program CID, etc.). Refer to the The
MultiMediaCard System Specification.
While a busy signal is on the MMC bus, the software can send only one of two commands:
• Send status command (CMD13).
• Disconnect command (CMD7).
If the software disconnects a card while it is in a busy state, the busy signal will be turned off and
the software can connect a different card. The software may not start another command sequence
on the same card while the card is busy.