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Hardware Description
ARM DUI 0224F Copyright © 2003-2007 ARM Limited. All rights reserved. 3-75
3.14 Memory Card Interface, MCI
Two ARM PL180 PrimeCell MCIs provide the interface to two multimedia (MMC) or
Secure Digital (SD) cards.
Each interface can be driven as either an MMC or SD interface.
3.14.1 MMC or SD operation
The MMC socket provides nine pins that connect to the card when it is inserted into the
socket. (The nine-way socket is compatible with SD cards. However MMC uses only
seven of the nine pins.)
The socket contains two switches that are operated by inserting or removing the card.
These are used to provide signaling on the nCARDIN and WPROT signals.
The function of the interface signals depends on whether an MMC or SD card is fitted.
Both card types default to MMC but the SD card has an additional operating mode
called widebus mode. Table 3-17 shows the use of the signals for both modes of
operation.
Table 3-17 MMC/SD interface signals
Signal Widebus mode (SD only) MMC mode (default)
MCIxDAT3 card detect/Data(3) chip select (active LOW)
MCIxCMD command/Response command/Response
MCIxCLK clock clock
MCIxDAT0 data (0) data
MCIxDAT1 data (1) not used
MCIxDAT2 data (2) not used
nCARDINx card presence detect (active LOW) card presence detect (active LOW)
WPROTx card write-protection detect card write-protection detect