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MMC_Protocol protocol

This protocol describes an abstract, untimed interface between an MMC controller and an MMC or SD card.

The protocol contains methods that must be implemented by the master (controller) and some that must be implemented by the slave (card). This protocol is used by the reference PL180 MCI and MMC models. for further information on the protocol implementation, see the source file, %PVLIB_HOME%\LISA\MMC_Protocol.lisa.

Use of this protocol assumes knowledge of the MultiMediaCard specification, available from the MultiMediaCard Association, www.mmca.org.

The protocol has these behaviors:

cmd
Commands are sent from the controller to the card using this behavior, which is implemented by the card model. The MMC command is sent with an optional argument. The card responds as defined by the MMC specification. The controller model checks that the response type matches expectations, and updates its state appropriately. The transaction-level protocol does not model start/stop bits or CRCs on the command/response payload.

For data transfer in the card to controller direction:

Rx
After the host and controller have initiated a read through the command interface, the card calls the Rx behavior on the controller to provide the read data. The call provides a pointer and a length. The ARM MMC reference model simulates device read latency by waiting a number of clock cycles prior to calling this behavior. If the controller is unable to accept the data, or wants to force a protocol error, it can return false in response to this behavior.
Rx_rdy
A handshake, used by the controller to inform the card that the controller is ready to receive more data. The ARM MMC reference model does not time out, so waits indefinitely for this handshake in a multiple block data transfer.

For data transfer in the controller to card direction:

Tx
After the host and controller have initiated a write through the command interface, the card calls the Tx behavior on the controller. The call provides a pointer to an empty buffer to be written, and a length. The ARM MMC reference model simulates device write latency by waiting a number of clock cycles prior to each buffer being offered.
Tx_done
The controller calls this behavior on the card when the block has been written. The card model can then commit the data to its persistent storage.

The card model must also implement:

cmd_name
This behavior returns the name of the command issued. A card must implement this behavior, but is free to return an empty string for all requests. Only call this behavior for diagnostic messages.
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