
RM0008
Secure digital input/output interface (SDIO)
Doc ID 13902 Rev 12
585/1096
Note:
1
While the SD/SDIO card or MultiMediaCard is in identification mode, the SDIO_CK
frequency must be less than 400 kHz.
2
The clock frequency can be changed to the maximum card bus frequency when relative
card addresses are assigned to all cards.
3
At least seven HCLK clock periods are needed between two write accesses to this register.
SDIO_CK can also be stopped during the read wait interval for SD I/O cards: in this case the
SDIO_CLKCR register does not control SDIO_CK.
22.9.3
SDIO argument register (SDIO_ARG)
Address offset: 0x08
Reset value: 0x0000 0000
The SDIO_ARG register contains a 32-bit command argument, which is sent to a card as
part of a command message.
Bit 10
BYPASS:
Clock divider bypass enable bit
0: Disable bypass: SDIOCLK is divided according to the CLKDIV value before driving the
SDIO_CK output signal.
1: Enable bypass: SDIOCLK directly drives the SDIO_CK output signal.
Bit 9
PWRSAV:
Power saving configuration bit
For power saving, the SDIO_CK clock output can be disabled when the bus is idle by setting
PWRSAV:
0: SDIO_CK clock is always enabled
1: SDIO_CK is only enabled when the bus is active
Bit 8
CLKEN:
Clock enable bit
0: SDIO_CK is disabled
1: SDIO_CK is enabled
Bits 7:0
CLKDIV:
Clock divide factor
This field defines the divide factor between the input clock (SDIOCLK) and the output clock
(SDIO_CK): SDIO_CK frequency = SDIOCLK / [ 2].
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1
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CMDARG
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Bits 31:0
CMDARG:
Command argument
Command argument sent to a card as part of a command message. If a command contains
an argument, it must be loaded into this register before writing a command to the command
register.