Intel PXA26X - Manual (Page 527)

Intel® PXA26x Processor Family Developer’s Manual 15-15
MultiMediaCard Controller
• 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
MultiMediaCard System Specification, Version 2.1.
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.
15.3.4 SPI Functionality
The MMC controller can address up to two cards in SPI mode using the MMCCS[1:0] chip select
signals. Once the software specifies which chip select to enable in the MMC_SPI register, the
selected signal is driven active low at a falling edge of the MMC clock. The chip select remains
asserted until software clears the chip select enable bit or selects another card.
Note: The clock must be stopped before writing to any registers as described in Section 15.3.1, “Basic,
No Data, Command and Response Sequence” .
In SPI mode, the software has the option of performing a CRC check. The default is no CRC
checking.
The command and data are sent on the MMC bus aligned to every 8 clocks as described in the SPI
section of the MultiMediaCard System Specification, Version 2.1.
In a read sequence, the card may return data or a data error token. If a data error token is received,
the controller will stop the transmission and update the status register.
15.4 MultiMediaCard Controller Operation
The software directs all communication between the card and the controller. The operations shown
in the preceding sections are valid for MMC mode only.