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RM0351 SD/SDIO/MMC card host interface (SDMMC)
1450
41.5 Response formats
All responses are sent via the SDMMC command line SDMMC_CMD. The response
transmission always starts with the left bit of the bit string corresponding to the response
code word. The code length depends on the response type.
A response always starts with a start bit (always 0), followed by the bit indicating the
direction of transmission (card = 0). A value denoted by x in the tables below indicates a
variable entry. All responses, except for the R3 response type, are protected by a CRC.
Every command code word is terminated by the end bit (always 1).
There are five types of responses. Their formats are defined as follows:
41.5.1 R1 (normal response command)
Code length = 48 bits. The 45:40 bits indicate the index of the command to be responded to,
this value being interpreted as a binary-coded number (between 0 and 63). The status of the
card is coded in 32 bits.
Table 242. Application-specific commands
CMD
index
Type Argument
Response
format
Abbreviation Description
CMD55 ac
[31:16] RCA
[15:0] stuff bits
R1 APP_CMD
Indicates to the card that the next command
bits is an application specific command rather
than a standard command
CMD56 adtc
[31:1] stuff bits
[0]: RD/WR
--
Used either to transfer a data block to the card
or to get a data block from the card for general
purpose/application-specific commands. The
size of the data block shall be set by the
SET_BLOCK_LEN command.
CMD57
...
CMD59
Reserved.
CMD60
...
CMD63
Reserved for manufacturer.
Table 243. R1 response
Bit position Width (bits Value Description
47 1 0 Start bit
46 1 0 Transmission bit
[45:40] 6 X Command index
[39:8] 32 X Card status
[7:1] 7 X CRC7
011 End bit
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