SanDisk SDSDB-32-201-80 - Industrial Grade Flash Memory Card Product Manual page 52

Secure Digital (SD) Card Protocol Description
From
host to
card(s)
Command
CMD
DAT
Block read operation
The block write operation uses a simple busy signaling of the write operation duration on the DAT0 data line (see
Figure 4-3) regardless of the number of data lines used for transferring the data.
From
host to
card
Command
CMD
DAT
Command tokens have the coding scheme shown in Figure 4-4.
Transmitter bit:
'1'=host command
Start bit
always '0'
0
Each command token is preceded by a start bit ('0') and succeeded by an end bit ('1'). The total length is 48 bits.
Each token is protected by CRC bits so that transmission errors can be detected and the operation may be repeated.
4-2
From
card to
host
Response
Data block crc
Multiple block read operation
Figure 4-2. Multiple Block Read Operation
From
card to
host
Response
Data block
Block write operation
Multiple block write operation
Figure 4-3. Multiple Block Write Operation
Command content: command and
address information or parameter,
protected by 7 bit CRC checksum
1 Content
Total length = 48 bits
Figure 4-4. Command Token Format
SanDisk Secure Digital (SD) Card Product Manual, Rev. 1.9 © 2003 SANDISK CORPORATION
Data from
card to host
Data block crc Data block
crc OK
Data
response
from card and busy
to host from card
Command
crc Busy Data block
CRC
Stop command
stops data transfer
Command Response
crc
Data stop operation
Stop
command
stops data
transfer
Response
Busy
crc
Data stop operation
End bt:
always '1'
1