RM0090: Reference manual - STMicroelectronics

RM0090 Secure digital input/output interface (SDIO)
28.5.4 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.
28.5.5 R4 (Fast I/O)
28.5.6 R4b
Table 151. 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
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.
Table 152. 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
For SD I/O only: an SDIO card receiving the CMD5 will respond with a unique SDIO
response R4. The format is:
Table 153. R4b response
Bit position Width (bits Value Description
47 1 0 Start bit
46 1 0 Transmission bit
[45:40] 6 x Reserved
Doc ID 018909 Rev 3 878/1416