MC56U032DCCA Datasheet, PDF (36/64 Pages) Samsung semiconductor – Dual Voltage MultiMediaCard Specification

MultiMediaCard^TM
Stand-by State. This command is used to identify new cards without resetting other already acquired
cards. Cards to which an RCA has already been assigned, do not respond to the identification
command flow in this state. All the data communication in the Data Transfer Mode is consequently a
point-to point communication between the host and the selected card (using addressed commands).
All addressed commands are acknowledged by a response on the CMD line. All read commands (data
is sent from the card via data lines) can be interrupted at any time, by a stop command. The data
transfer will terminate and the card will stop or start working on the next command. The DAT bus line
signal level is high when no data is transmitted. A transmitted data block consists of a start bit (LOW),
followed by a continuous data stream.
The data stream contains the net payload data (and error correction bits if an off-card ECC is used).
The data stream ends with an end bit (HIGH). The data transmission is synchronous to the clock signal.
The payload for block-oriented data transfer is preserved by a CRC check sum (refer to Chapter
“Cyclic Redundancy Check (CRC)”).
4.9.1 Block Read
The basic unit of data transfer is a block whose maximum size is defined in the CSD
(READ_BLK_LEN). A CRC is appended to the end of each block ensuring data transfer integrity.
READ_SINGLE_BLOCK (CMD17) starts a block read and after a complete transfer the card goes back
to Transfer State. READ_MULTIPLE_BLOCK (CMD18) starts a transfer of several consecutive blocks.
Two types of multiple block read transactions are defined (the host can use either one at any time):
* Open-ended Multiple block read : The number of blocks for the read multiple block operation is not
defined. The card will continuously transfer data blocks until a stop transmission command is
received.
* Multiple block read with pre-defined block count : The card will transfer the requested number of
data blocks, terminate the transaction and return to transfer state. Stop command is not required at
the end of this type of multiple block read, unless terminated with an error. In other to start multiple
block read with pre-defined block count, the host must use the SET_BLOCK COUNT
command(CMD23) immediately preceding the READ_MULTIPLE_BLOCK(CMD18) command.
Otherwise this card will start an open-ended multiple block read which can be stopped using the
STOP_TRANSMISSION command.
4.9.2 Block Write
Block write (CMD24 - 27) means that one or more blocks of data are transferred from the host to the
card with a CRC appended to the end of each block by the host. A card supporting block write must
always be able to accept a block of data defined by WRITE_BLK_LEN. If the CRC fails, the card will
indicate the failure on the DAT line; the transferred data will be discarded and not written and all further
transmitted blocks (in multiple block write mode) will be ignored. The write operation will also be
aborted if the host tries to write over a write-protected area. In this case, however, the card will set the
WP_VIOLATION bit. Programming of the CID and CSD register does not require a previous block
length setting. The transferred data is also CRC protected. The MultiMediaCard write operation follows
some special rules:
WRITE_MULTIPLE_BLOCK(CMD25) starts a transfer of several consecutive blocks. Two types of
multiple block write transactions, identical to the multiple block read, are defined (the host can use
either on at any time)
* Open-ended Multiple block write : The number of blocks for the write multiple block operation is not
defined. The card will continuously accept and program data block until a stop transmission
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