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.

15.3.2.4Stream 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.

15.3.3Busy 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.

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Intel® PXA255 Processor Developer’s Manual

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Intel PXA255 manual Busy Sequence, Stream Data Read