Multimedia Card Registers
Table 18-29. SD_CMD Register Field Descriptions (continued)
Bit
Field
Type
Reset
Description
5
MSBS
R/W
0h
Multi/Single block select.
This bit must be set to 1 for data transfer in case of multi block
command.
For any others command this bit shall be cleared to 0.
0x0 = Single block. If this bit is 0, it is not necessary to set the
register SD_BLK[31:16] NBLK bits.
0x1 = Multi block. When Block Count is disabled (SD_CMD[1] BCE
bit is cleared to 0) in Multiple block transfers (SD_CMD[5] MSBS bit
is set to 1), the module can perform infinite transfer.
4
DDIR
R/W
0h
Data transfer Direction.
Select This bit defines either data transfer will be a read or a write.
0x0 = Data Write (host to card)
0x1 = Data Read (card to host)
3
Reserved
R
0h
2
ACEN
R/W
0h
Auto CMD12 Enable (SD cards only).
When this bit is set to 1, the host controller issues a CMD12
automatically after the transfer completion of the last block.
The Host Driver shall not set this bit to issue commands that do not
require CMD12 to stop data transfer.
In particular, secure commands do not require CMD12.
For CE-ATA commands (SD_CON[12] CEATA bit set to 1), auto
CMD12 is useless
therefore when this bit is set the mechanism to detect command
completion signal, named CCS, interrupt is activated.
0x0 = Auto CMD12 disable
0x1 = Auto CMD12 enable or CCS detection enabled.
1
BCE
R/W
0h
Block Count Enable (Multiple block transfers only).
This bit is used to enable the block count register (SD_BLK
[31:16] NBLK bits).
When Block Count is disabled (SD_CMD[1] BCE bit is cleared to 0)
in Multiple block transfers (SD_CMD[5] MSBS bits is set to 1), the
module can perform infinite transfer.
0x0 = Block count disabled for infinite transfer.
0x1 = Block count enabled for multiple block transfer with known
number of blocks
0
DE
R/W
0h
DMA Enable.
This bit is used to enable DMA mode for host data access.
0x0 = DMA mode disable
0x1 = DMA mode enable
3410
Multimedia Card (MMC)
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated