Secure Digital (SD) Card Protocol Description
SanDisk Secure Digital (SD) Card Product Manual, Rev. 1.9 © 2003 SANDISK CORPORATION
4-9
Data-transfer
mode
From all states in
data-transfer mode
No state transition
in data-transfer mode
Card Identification
mode
CMD4,
9, 10
CMD12
"operation
complete"
CMD17, 18, 30, 56(r)
ACMD51
CMD24, 25, 26,
27, 42, 56(w)
CMD28,
29, 38
CMD 16, 32...37
ACMD6, 13, 42
ACMD 22,23
CMD3
CMD13, CMD55
CMD7
CMD7
"Operation
complete"
"Operation
complete"
CMD15
CMD0
Sending-data
state (data)
Receive-data
state (rcv)
Disconnect
state (dis)
Programming
state (prg)
Transfer
state (tran)
Stand-by state
(stby)
CMD12 or
"transfer end"
"Operation
complete"
CMD7
CMD7
Figure 4-8. SD Card State Diagram (Data Transfer Mode)
CMD7 is used to select one SD Card and place it in the Transfer State. Only one SD Card can be in the Transfer
State at a given time. If a previously selected SD Card is in the Transfer State, its connection with the host is
released and it will move back to the Stand-by State. When CMD7 is issued with the reserved relative card address
“0x0000,” all cards transfer back to Stand-by State. (Note that it is the responsibility of the Host to reserve the
RCA=0 for card de-selection—refer to Table 4-3, CMD7 description). This may be used before identifying new
cards without resetting other already registered cards. Cards that already have an RCA do not respond to
identification commands (ACMD41, CMD2, CMD3) in this state.
Important Note: The card de-selection is done if a certain card gets CMD7 with un-matched RCA. That happens
automatically if selection is done to another card and the
CMD lines are common
. So, in the SD Card system, it will
be the responsibility of the host either:
•
To work with the common CMD line (after initialization is done). In this case the card de-selection
will be done automatically (as in MultiMediaCard system).
•
If the CMD lines are separate, to be aware of the necessity to deselect cards.
All data communication in the Data Transfer Mode is point-to point between the host and the selected SD Card
(using addressed commands). All addressed commands are acknowledged with a response on the CMD line.
The relationship between the various data transfer modes is summarized in Figure 4-8, and in the following
paragraphs: