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
011 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
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