SDIO

Commands Table

CMD Index	Type	Argument	Response	Abbreviation	Command Description
CMD0	bc	[31:0] stuff bits		GO_IDLE_STATE	Resets all cards to idle state.
CMD2	bcr	[31:0] stuff bits	R2	ALL_SEND_CID	Asks any card to send the CID num-bers on the CMD line (any card that is connected to the host will respond).
CMD6
CMD7	ac		R1b (only from the selected card)	SELECT/DESELECT_CARD
CMD8	bcr	[31:12] reserved bits [11:8] supply voltage(VHS) [7:0] check pattern	R7	SEND_IF_COND	Sends SD Memory Card interface condition, which includes host supply voltage information and asks the card whether card supports voltage. Reserved bitsshall be set to '0'.
CMD9	ac	[31:16] RCA [15:0] stuff bits	R2	SEND_CSD	Addressed card sends its card-specific data (CSD) on the CMD line.
CMD12	ac	[31:0] stuff bits	R1b	STOP_TRANSMISSION	Forces the card to stop transmission.
CMD16	ac	[31:0] block length	R1	SET_BLOCKLEN	In the case of a Standard Capacity SD Memory Card, this command sets the block length (in bytes) for all following block commands (read, write, lock). Default block length is fixed to 512Bytes. Set length is valid for memory access commands only if partial block read operation are allowed in CSD.
CMD17	adtc	[31:0] data address	R1	READ_SINGLE_BLOCK	In the case of a Standard Capacity SD Memory Card, this command, this command reads a block of the size selected by the SET_BLOCKLEN command. In case of SDHC and SDXC Cards, block length is fixed 512Bytes regardless of the SET_BLOCKLEN command.
CMD18	adtc	[31:0] data address	R1	READ_MULTIPLE_BLOCK	Continuously transfers data blocks from card to host until interrupted by a STOP_TRANSMISSION command.
CMD41
CMD55

Responses

R1 (normal response command)

R1 is a 48-bit response.

Linux flags:

• MMC_RSP_CRC

Bit position	47	46	[45:40]	[39:8]	[7:1]	0
Width (bits)	1	1	6	32	7	1
Value	'0'	'0'	x	x	x	'1'
Description	start bit	transmission bit	command index	card status	CRC7	end bit

R1b

R1b is a 48-bit response.

R2 (CID, CSD register)

R2 is a 136-bit response.

Linux flags:

• MMC_RSP_136

R3 (OCR register)

R3 is a 48-bit response.

Bit position	47	46	[45:40]	[39:8]	[7:1]	0
Width (bits)	1	1	6	32	7	1
Value	'0'	'0'	'111111'	x	'1111111'	'1'
Description	start bit	transmission bit	reserved	OCR register	reserved	end bit

R6 (Published RCA response)

R6 is a 48-bit response.

R7 (Card interface condition)

R7 is a 48-bit response.

References

SD Specifications Part E1 SDIO Simplified Specification	http://academy.cba.mit.edu/classes/networking_communications/SD/SD.pdf