SanDisk SDSDH-1024 Product Manual - Page 47

Response Token Format, Data Packet Format

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Revision 2.2 Chapter 4 - SD Card Protocol Description SanDisk SD Card Product Manual Each command token is preceded by a start bit (0) and succeeded by an end bit (1). The total length is 48 bits. CRC bits protect each token to detect transmission errors; the operation may be repeated. Response tokens have four coding schemes depending on their content. The token length is either 48 or 136 bits. The CRC protection algorithm for block data is a 16-bit CCITT polynomial. All used CRC types are described in Section 4.6 Figure 4-5 Response Token Format "Transmitter" bit: 1=card response "Start" bit always 0 Response-content mirrored command and status information (R1 response). OCR Register (R3 response) or RCA (R6) protected by 7-bit CRC checksum "End" bit always 1 00 Content 1 R1, R3, R6 Total length = 48 bits "End" bit always 1 R2 0 0 Content= CID or CSD Total length = 136 bits CRC 1 In the CMD line, the MSB bit is transmitted first, whereas the LSB bit is transmitted last. When the wide-bus option is used, the data is transferred four bits at a time (see Figure 46). Start and end bits, as well as the CRC bits, are transmitted for every one of the DAT lines. CRC bits are calculated and checked for every DAT line individually. The card sends the host the CRC status response and busy indication on DAT0 only. (DAT1-DAT3 during that period is "don't care"). Figure 4-6 Data Packet Format "Start" bit always 0 MSB (4095) LSB (0) "End" bit always 1 Standard busy 0 (only DAT0 used) MSN Wide bus (all four data lines used) DAT3 0 4095 DAT2 0 4094 DAT1 0 4093 DAT0 0 4092 Block length Block length /4 CRC 1 "End" bit always 1 LSN 3 CRC 1 2 CRC 1 1 CRC 1 0 CRC 1 © 2004 SanDisk Corporation 4-3 12/08/04

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Chapter 4 – SD Card Protocol Description
Revision 2.2
SanDisk SD Card Product Manual
© 2004 SanDisk Corporation
4-3
12/08/04
Each command token is preceded by a start bit (0) and succeeded by an end bit (1). The
total length is 48 bits. CRC bits protect each token to detect transmission errors; the
operation may be repeated.
Response tokens have four coding schemes depending on their content. The token length is
either 48 or 136 bits. The CRC protection algorithm for block data is a 16-bit CCITT
polynomial. All used CRC types are described in Section 4.6
Figure 4-5
Response Token Format
In the CMD line, the MSB bit is transmitted first, whereas the LSB bit is transmitted last.
When the wide-bus option is used, the data is transferred four bits at a time (see Figure 4-
6). Start and end bits, as well as the CRC bits, are transmitted for every one of the DAT
lines. CRC bits are calculated and checked for every DAT line individually. The card sends
the host the CRC status response and busy indication on DAT0 only. (DAT1-DAT3 during
that period is “don’t care”).
Figure 4-6
Data Packet Format
"Start" bit
always 0
"End" bit
always 1
Response-content mirrored command and
status information (R1 response). OCR Register
(R3 response) or RCA (R6) protected by 7-bit
CRC checksum
"Transmitter" bit:
1=card response
Total length = 48 bits
0
Content
0
1
Total length = 136 bits
0
Content= CID or CSD
CRC
0
1
"End" bit
always 1
R1, R3, R6
R2
"Start" bit
always 0
"End" bit
always 1
MSB (4095)
Block length
0
Block length /4
"End" bit
always 1
LSB (0)
Standard busy
(only DAT0 used)
CRC
1
DAT3
0
CRC
4095
1
3
DAT2
0
CRC
4094
1
2
DAT1
0
CRC
4093
1
1
DAT0
0
CRC
4092
1
0
MSN
LSN
Wide
bus (all
four data
lines
used)