Secure Digital (SD) Card Protocol Description
4-2
SanDisk Secure Digital (SD) Card Product Manual, Rev. 1.9 © 2003 SANDISK CORPORATION
From
host to
card(s)
CMD
DAT
Command
Data from
card to host
Command
Response
From
card to
host
Block read operation
Multiple block read operation
Response
Data stop operation
Data block crc
Data block crc
Data block crc
Stop command
stops data transfer
Figure 4-2. Multiple 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
CMD
DAT
Command
Data
from card
to host
Command
Response
From
card to
host
Block write operation
Multiple block write operation
Response
Data stop operation
Data block crc
Data block crc
Busy
Stop
command
stops data
transfer
Busy
crc OK
response
and busy
from card
Figure 4-3. Multiple Block Write Operation
Command tokens have the coding scheme shown in Figure 4-4.
Start bit
always '0'
0 1 Content CRC 1
Command content: command and
address information or parameter,
protected by 7 bit CRC checksum
Transmitter bit:
'1'=host command
Total length = 48 bits
End bt:
always '1'
Figure 4-4. Command Token Format
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.
