
SD/SDIO/MMC card host interface (SDMMC)
RM0351
1556/1830
DocID024597 Rev 5
45.5.4 R3
(OCR
register)
Code length: 48 bits. The contents of the OCR register are sent as a response to CMD1.
The level coding is as follows: restricted voltage windows = low, card busy = low.
45.5.5
R4 (Fast I/O)
Code length: 48 bits. The argument field contains the RCA of the addressed card, the
register address to be read out or written to, and its content.
45.5.6 R4b
For SD I/O only: an SDIO card receiving the CMD5 will respond with a unique SDIO
response R4. The format is:
Table 290. R3 response
Bit position
Width (bits
Value
Description
47
1
0
Start bit
46
1
0
Transmission bit
[45:40]
6
‘111111’
Reserved
[39:8]
32
X
OCR register
[7:1]
7
‘1111111’
Reserved
0
1
1
End bit
Table 291. R4 response
Bit position
Width (bits
Value
Description
47
1
0
Start bit
46
1
0
Transmission bit
[45:40]
6
‘100111’
CMD39
[39:8] Argument field
[31:16]
16
X
RCA
[15:8]
8
X
register address
[7:0]
8
X
read register contents
[7:1]
7
X
CRC7
0
1
1
End bit
Table 292. R4b response
Bit position
Width (bits
Value
Description
47
1
0
Start bit
46
1
0
Transmission bit
[45:40]
6
X
Reserved