Datasheet

06 February 2012 Broadcom Europe Ltd. 406 Science Park Milton Road Cambridge CB4 0WW Page 69
© 2012 Broadcom Corporation. All rights reserved
CMDTM Register
Synopsis
This register is used to issue commands to the card. Besides the command it also
contains flags informing the EMMC module what card response and type of data
transfer to expect. Incorrect flags will result in strange behaviour.
For data transfers two modes are supported: either transferring a single block of data
or several blocks of the same size. The SD card uses two different sets of commands
to differentiate between them but the host needs to be additionally configured using
TM_MULTI_BLOCK. It is important that this bit is set correct for the command sent to
the card, i.e. 1 for CMD18 and CMD25 and 0 for CMD17 and CMD24. Multiple block
transfer gives a better performance.
The BLKSIZECNT register is used to configure the size and number of blocks to be
transferred. If bit TM_BLKCNT_EN of this register is set the transfer stops
automatically after the number of data blocks configured in the BLKSIZECNT register
has been transferred.
The TM_AUTO_CMD_EN bits can be used to make the host to send automatically a
command to the card telling it that the data transfer has finished once the BLKCNT bits
in the BLKSIZECNT register are 0.
Bit(s)
Field Name
Description
Type
Reset
31:30
Reserved
-
Write as 0, read as don't care
29:24 CMD_INDEX Index of the command to be issued to the card RW 0x0
23:22 CMD_TYPE Type of command to be issued to the card:
00 = normal
01 = suspend (the current data transfer)
10 = resume (the last data transfer)
11 = abort (the current data transfer)
RW 0x0
21 CMD_ISDATA Command involves data transfer:
0 = no data transfer command
1 = data transfer command
RW 0x0
20 CMD_IXCHK_EN Check that response has same index as
command:
0 = disabled
1 = enabled
RW 0x0
19 CMD_CRCCHK_EN Check the responses CRC:
0 = disabled
1 = enabled
RW 0x0
18
Reserved
-
Write as 0, read as don't care
17:16 CMD_RSPNS_TYPE Type of expected response from card:
00 = no response
01 = 136 bits response
10 = 48 bits response
11 = 48 bits response using busy
RW 0x0