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GD32F403xx User Manual
520
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R7 :
Card interface condition.
The SD Memory Card support five types of them, R1 / R1b, R2, R3, R6, R7. And the SD I/O
Card and MMC supports additional response types named R4 and R5, but they are not exactly
the same for SD I/O Card and MMC.
Responses format
Responses have two formats, as show in
Figure 20-8. Response Token Format
,
all
responses are sent on the CMD line. The code length depends on the response type. Except
R2 is 136 bits length, others are all 48 bits length.
Figure 20-8. Response Token Format
0
1
Content
CRC
1
Total length = 48 bits
0
1
Content = CID or CSD
CRC
1
Total length = 136 bits
A response always starts with a start bit (always 0), followed by the bit indicating the direction
of transmission (card = 0). A value ‘x’ in the tables below indicates a variable entry. All
responses except for the type R3 are protected by a CRC. Every command code word is
terminated by the end bit (always 1).
R1 (normal response command)
Code length is 48 bits. The bits 45:40 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. Note that if a data transfer to the card is involved, then a busy signal
may appear on the data line after the transmission of each block of data. The host shall check
for busy after data block transmission. The card status is described in
Table 20-14. Response R1
Bit position
47
46
[45:40]
[39:8]
[7:1]
0
Width
1
1
6
32
7
1
Value
‘0’
‘0’
x
x
x
‘1’
description
start bit
transmission
bit
command
index
card
status
CRC7
end bit
R1b
R1b is identical to R1 with an optional busy signal transmitted on the data line DAT0. The
card may become busy after receiving these commands based on its state prior to the
command reception. The Host shall check for busy at the response.