Chapter 4 – SD Card Protocol Description
Revision 2.2 SanDisk SD Card Product Manual
© 2004 SanDisk Corporation 4-43 12/08/04
Data Transfer Mode
There is just one Z bit period followed by P bits pushed up by the responding card. This
timing diagram is relevant for all responded host commands except CMD1, 2, 3.
Command Response Timing (Data Transfer Mode)
Last Card Response—Next Host Command Timing
After receiving the last card response, the host can start the next command transmission
after at least N
RC
clock cycles. This timing is relevant for any host command.
Timing Response End to Next CMD Start (Data Transfer Mode)
Last Host Command—Next Host Command Timing
After the last command has been sent, the host can continue sending the next command
after at least N
CC
clock periods.
Timing of Command Sequences (All modes)
4.11 Data Read
Single Block Read
The host selects one card for data read operation by CMD7 and sets the valid block length
for block-oriented data transfer by CMD16. The basic bus timing for a read operation is
shown in the Transfer of Single Block Read timing diagram. The sequence starts with a
single block read command, CMD17 that specifies the start address in the argument field.
The response is sent on the CMD line as usual.
Transfer of Single Block Read
Data transmission from the card starts after the access time delay N
AC
beginning from the
end bit of the read command. After the last data bit, the CRC check bits are suffixed to
allow the host to check for transmission errors.
CMD S T Content E Z ****** Z S T Z
Host Command N
CC
CRC
Host Command
Cycles
Content CRC E
CMD S T Content E Z *** P S TCRC
Response
Cycles
Content CRC EZ P
DAT
Z Z **** Z Z **********Z P S D
N
AC
Read DataCycles
DZ Z Z Z P D ***
CMD S T Content E Z *** P S T Z Z Z
Host Command N
CR
CRC
Response
Cycles
Content CRC ZEZ P
CMD S T Content E Z ****** Z S T Z
Response N
RC
CRC
Host Command
Cycles
Content CRC E
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