Multimedia Card Registers
Table 18-36. SD_HCTL Register Field Descriptions (continued)
Bit
Field
Type
Reset
Description
19
IBG
R/W
0h
Interrupt block at gap.
This bit is valid only in
4-bit mode of SDIO card to enable interrupt detection in the interrupt
cycle at block gap for a multiple block transfer.
For MMC cards and for SD card this bit should be cleared to 0.
0x0 = Disable interrupt detection at the block gap in 4-bit mode
0x1 = Enable interrupt detection at the block gap in 4-bit mode
18
RWC
R/W
0h
Read wait control.
The read wait function is optional only for SDIO cards.
If the card supports read wait, this bit must be enabled, then
requesting a stop at block gap (SD_HCTL[16] SBGR bit) generates a
read wait period after the current end of block.
Be careful, if read wait is not supported it may cause a conflict on
mmc_dat line.
0x0 = Disable read wait control. Suspend/resume cannot be
supported.
0x1 = Enable read wait control
17
CR
R/W
0h
Continue request.
This bit is used to restart a transaction that was stopped by
requesting a stop at block gap (SD_HCTL[16] SBGR bit).
Set this bit to 1 restarts the transfer.
The bit is automatically cleared to 0 by the host controller when
transfer has restarted, that is, mmc_dat line is active
(SD_PSTATE[2] DLA bit) or transferring data (SD_PSTATE[8] WTA
bit).
The Stop at block gap request must be disabled (SD_HCTL[16]
SBGR bit =0) before setting this bit.
0x0 = No affect
0x1 = Transfer restart
16
SBGR
R/W
0h
Stop at block gap request.
This bit is used to stop executing a transaction at the next block gap.
The transfer can restart with a continue request (SD_HCTL[17] CR
bit) or during a suspend/resume sequence.
In case of read transfer, the card must support read wait control.
In case of write transfer, the host driver shall set this bit after all
block data written.
Until the transfer completion (SD_STAT[1] TC bit set to 1), the host
driver shall leave this bit set to 1.If this bit is set, the local host shall
not write to the data register (SD_DATA).
0x0 = Transfer mode
0x1 = Stop at block gap
15-12
Reserved
R
0h
11-9
SDVS
R/W
0h
SD bus voltage select (All cards).
The host driver should set these bits to select the voltage level for
the card according to the voltage supported by the system
(SD_CAPA[26] VS18 bit, SD_CAPA[25] VS30 bit, SD_CAPA[24]
VS33 bit) before starting a transfer.
If MMCHS
2: This field must be set to 5h.
If MMCHS
3: This field must be set to 5h.
0x5 = 1.8 V (Typical)
0x6 = 3.0 V (Typical)
0x7 = 3.3 V (Typical)
3420
Multimedia Card (MMC)
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated