Multimedia Card Registers
Table 18-37. SD_SYSCTL Register Field Descriptions (continued)
Bit
Field
Type
Reset
Description
24
SRA
R/W
0h
Software reset for all.
This bit is set to 1 for reset , and released to 0 when completed.
This reset affects the entire host controller except for the card
detection circuit and capabilities registers.
0x0 = Reset completed
0x1 = Software reset for all the design
23-20
Reserved
R
0h
19-16
DTO
R/W
0h
Data timeout counter value and busy timeout.
This value determines the interval by which mmc_dat lines timeouts
are detected.
The host driver needs to set this bit field based on: The maximum
read access time (NAC) (Refer to the SD Specification Part1
Physical Layer).
The data read access time values (TAAC and NSAC) in the card
specific data register (CSD) of the card.
The timeout clock base frequency (SD_CAPA
[5:0] TCF bits).
If the card does not respond within the specified number of cycles, a
data timeout error occurs (SD_STAT[20] DTO bit).
The SD_SYSCTL[19,16] DTO bit field is also used to check busy
duration, to generate busy timeout for commands with busy
response or for busy programming during a write command.
Timeout on CRC status is generated if no CRC token is present after
a block write.
0x0 = TCF x 2^13
0x1 = TCF x 2^14
0xe = TCF x 2^27
0xf = Reserved
15-6
CLKD
R/W
0h
Clock frequency select.
These bits define the ratio between a reference clock frequency
(system dependant) and the output clock frequency on the mmc_clk
pin of either the memory card (MMC, SD, or SDIO).
0x0 = Clock Ref bypass
0x1 = Clock Ref bypass
0x2 = Clock Ref / 2
0x3 = Clock Ref / 3
0x3ff = Clock Ref / 1023
5-3
Reserved
R
0h
2
CEN
R/W
0h
Clock enable.
This bit controls if the clock is provided to the card or not.
0x0 = The clock is not provided to the card . Clock frequency can be
changed .
0x1 = The clock is provided to the card and can be automatically
gated when SD_SYSCONFIG[0] AUTOIDLE bit is set to 1 (default
value). The host driver shall wait to set this bit to 1 until the Internal
clock is stable (SD_SYSCTL[1] ICS bit).
1
ICS
R
0h
Internal clock stable (status)This bit indicates either the internal clock
is stable or not.
0x0 = The internal clock is not stable.
0x1 = The internal clock is stable after enabling the clock
(SD_SYSCTL[0] ICE bit) or after changing the clock ratio
(SD_SYSCTL[15:6] CLKD bits).
0
ICE
R/W
0h
Internal clock enable.
This register controls the internal clock activity.
In very low power state, the internal clock is stopped.
NoteThe activity of the debounce clock (used for wake-up events)
and the interface clock (used for reads and writes to the module
register map) are not affected by this register.
0x0 = The internal clock is stopped (very low power state).
0x1 = The internal clock oscillates and can be automatically gated
when SD_SYSCONFIG[0] AUTOIDLE bit is set to 1 (default value).
3423
SPRUH73H – October 2011 – Revised April 2013
Multimedia Card (MMC)
Copyright © 2011–2013, Texas Instruments Incorporated