RM0368 Datasheet, PDF (616/841 Pages) STMicroelectronics – This Reference manual targets application developers

Secure digital input/output interface (SDIO)
RM0368
Bit position
47
46
[45:40]
[39:8]
[7:1]
0
Table 96. Short response format
Width
Value
Description
1
0
Start bit
1
0
6
-
32
-
7
-
Transmission bit
Command index
Argument
CRC7(or 1111111)
1
1
End bit
Bit position
135
134
[133:128]
[127:1]
0
Table 97. Long response format
Width
Value
Description
1
0
Start bit
1
0
Transmission bit
6
111111
Reserved
127
-
CID or CSD (including internal CRC7)
1
1
End bit
The command register contains the command index (six bits sent to a card) and the
command type. These determine whether the command requires a response, and whether
the response is 48 or 136 bits long (see Section 21.9.4 on page 651). The command path
implements the status flags shown in Table 98:
Flag
CMDREND
CCRCFAIL
CMDSENT
CTIMEOUT
CMDACT
Table 98. Command path status flags
Description
Set if response CRC is OK.
Set if response CRC fails.
Set when command (that does not require response) is sent
Response timeout.
Command transfer in progress.
The CRC generator calculates the CRC checksum for all bits before the CRC code. This
includes the start bit, transmitter bit, command index, and command argument (or card
status). The CRC checksum is calculated for the first 120 bits of CID or CSD for the long
response format. Note that the start bit, transmitter bit and the six reserved bits are not used
in the CRC calculation.
The CRC checksum is a 7-bit value:
CRC[6:0] = Remainder [(M(x) * x⁷) / G(x)]
G(x) = x⁷ + x³ + 1
M(x) = (start bit) * x³⁹ + ... + (last bit before CRC) * x⁰, or
M(x) = (start bit) * x¹¹⁹ + ... + (last bit before CRC) * x⁰
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