ARM Technical Support Knowledge Articles

Section 2.5. MMCI Commands

Applies to: PL181 Multimedia Card Interface V2

Answer

Can the command, control bits and enable bit be written to MMCICommand in a single write, or should the command be setup first, and then the enable bit be set in a second write operation?

A single write can be used.

CMDOUT and CMDEN macro signal x command line should support both open-drain mode (card initialization) and push-pull: is this dual mode supported/managed internally to the macro-cell itself or has to be done outside?

Support for both modes is built in the peripheral.

push-pull:

CMD path is inactive -> nCMDEN=1

CMD is LOW           -> CMDOUT=0 and nCMDEN=0

CMD is HIGH          -> CMDOUT=1 and nCMDEN=0

open drain:

CMD path is inactive -> nCMDEN=1

CMD is LOW           -> CMDOUT=0 and nCMDEN=0

CMD is HIGH          -> CMDOUT=0 and nCMDEN=1

Is this done internally and should CMDOUT be connected to the output section of a bidirectional pad with enable driven by nCMDEN (nCMDEN = 0 -> CMD line is output)?

Correct,

nCMDEN=0 -> CMD output driver is active

nCMDEN=1 -> CMD output driver is in HI-Z

Article last edited on: 2008-09-09 15:47:25

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