Rainbow Electronics AT91CAP9S250A - Manual (Page 759)

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6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
41. MultiMedia Card Interface (MCI)
41.1 Description
The MultiMedia Card Interface (MCI) supports the MultiMedia Card (MMC) Specification
V3.11, the SDIO Specification V1.1 and the SD Memory Card Specification V1.0.
The MCI includes a command register, response registers, data registers, timeout counters
and error detection logic that automatically handle the transmission of commands and, when
required, the reception of the associated responses and data with a limited processor
overhead.
The MCI supports stream, block and multi-block data read and write, and is compatible with
the Peripheral DMA Controller (PDC) channels, minimizing processor intervention for large
buffer transfers.
The MCI operates at a rate of up to Master Clock divided by 2 and supports the interfacing of
1 slot(s). Each slot may be used to interface with a MultiMediaCard bus (up to 30 Cards) or
with a SD Memory Card. Only one slot can be selected at a time (slots are multiplexed). A bit
field in the SD Card Register performs this selection.
The SD Memory Card communication is based on a 9-pin interface (clock, command, four
data and three power lines) and the MultiMedia Card on a 7-pin interface (clock, command,
one data, three power lines and one reserved for future use).
The SD Memory Card interface also supports MultiMedia Card operations. The main differ-
ences between SD and MultiMedia Cards are the initialization process and the bus topology.