R3 (Ocr Register); R4 (Fast I/O); R4B; Table 186. R3 Response - ST STM32F412 Reference Manual

RM0402
27.5.4

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
27.5.5

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
27.5.6

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]
Width (bits
1
1
6
32
7
1
Bit position
[31:16]
[15:8]
[7:0]
Bit position
Secure digital input/output interface (SDIO)

Table 186. R3 response

Value
0
0
'111111'
X
'1111111'
1

Table 187. R4 response

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

Table 188. R4b response

Width (bits
1 0
1 0
6 X
RM0402 Rev 6
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
901/1163
921