R3 (Ocr Register); R4 (Fast I/O); R4B; Table 206. R3 Response - ST STM32F446 Series Reference Manual

Secure digital input/output interface (SDIO)
29.5.4

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.
Bit position
47
46
[45:40]
[39:8]
[7:1]
0
29.5.5

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.
47
46
[45:40]
[39:8] Argument field
[7:1]
0
29.5.6

R4b

For SD I/O only: an SDIO card receiving the CMD5 will respond with a unique SDIO
response R4. The format is:
47
46
[45:40]
1012/1328
Width (bits
1
1
6
32
7
1
Bit position
[31:16]
[15:8]
[7:0]
Bit position

Table 206. R3 response

Value
0
0
'111111'
X
'1111111'
1

Table 207. R4 response

Width (bits
1 0
1 0
6 '100111'
16 X
8 X
8 X
7 X
1 1

Table 208. R4b response

Width (bits
1 0
1 0
6 X
RM0390 Rev 4
Description
Start bit
Transmission bit
Reserved
OCR register
Reserved
End bit
Value Description
Start bit
Transmission bit
CMD39
RCA
register address
read register contents
CRC7
End bit
Value Description
Start bit
Transmission bit
Reserved
RM0390