AT32AP7000_1 Datasheet, PDF (579/973 Pages) ATMEL Corporation – AVR32 32-bit Microcontroller

AT32AP7000
30.7.2 MultiMedia Card Operations
30.7.2.1
After a power-on reset, the cards are initialized by a special message-based MultiMedia Card
bus protocol. Each message is represented by one of the following tokens:
• Command: A command is a token that starts an operation. A command is sent from the host
either to a single card (addressed command) or to all connected cards (broadcast command).
A command is transferred serially on the CMD line.
• Response: A response is a token which is sent from an addressed card or (synchronously)
from all connected cards to the host as an answer to a previously received command. A
response is transferred serially on the CMD line.
• Data: Data can be transferred from the card to the host or vice versa. Data is transferred via
the data line.
Card addressing is implemented using a session address assigned during the initialization
phase by the bus controller to all currently connected cards. Their unique CID number identifies
individual cards.
The structure of commands, responses and data blocks is described in the MultiMedia-Card
System Specification. See also Table 30-4 on page 580.
MultiMediaCard bus data transfers are composed of these tokens.
There are different types of operations. Addressed operations always contain a command and a
response token. In addition, some operations have a data token; the others transfer their infor-
mation directly within the command or response structure. In this case, no data token is present
in an operation. The bits on the DAT and the CMD lines are transferred synchronous to the MCI
Clock.
Two types of data transfer commands are defined:
• Sequential commands: These commands initiate a continuous data stream. They are
terminated only when a stop command follows on the CMD line. This mode reduces the
command overhead to an absolute minimum.
• Block-oriented commands: These commands send a data block succeeded by CRC bits.
Both read and write operations allow either single or multiple block transmission. A multiple
block transmission is terminated when a stop command follows on the CMD line similarly to the
sequential read or when a multiple block transmission has a predefined block count (See ”Data
Transfer Operation” on page 581.).
The MCI provides a set of registers to perform the entire range of MultiMedia Card operations.
Command - Response Operation
After reset, the MCI is disabled and becomes valid after setting the MCIEN bit in the Control
Register(CR).
The two bits RDPROOF and WRPROOF in the Mode Register (MR) allow stopping the MCI
Clock during read or write access if the internal FIFO is full. This will guarantee data integrity, not
bandwidth.
The command and the response of the card are clocked out with the rising edge of the MCI
Clock.
All the timings for MultiMedia Card are defined in the MultiMediaCard System Specification.
32003M–AVR32–09/09
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