Chapter 4 – SD Card Protocol Description
Revision 2.2
SanDisk SD Card Product Manual
© 2004 SanDisk Corporation
4-21
12/08/04
Figure 4-9
Use of Switch Command
CMD6 supports six function groups, and each function group supports 16 branches
(functions). Only one function can be chosen and active in a given function group.
Function 0 in each function group is the default function (compatible with v1.01).
CMD6 can be used in two modes.
•
Mode 0—Check Function
−
Check function is used to query if the card supports a specific function or
functions
•
Mode 1—Set Function
−
Set function is used to switch the functionality of the card.
Mode 0 Operation—Check Function
CMD6 is used in Mode 0 to query which functions the card supports, and to identify the
maximum current consumption of the card under the selected functions.
A query is accomplished by setting the argument field of the command.
1.
Set mode bit to 0.
2. Select only one function in each function group. Setting the function to 0x0 selects
the default function. Use appropriate values from Table 4-3 to selecting a specific
function. Selecting 0xF will keep the current function that was selected for the
function group.
In response to a query, the switch function status will return the following.
−
Functions not supported by each of the function groups
−
Function the card will switch to, in each of the function groups. This value is
identical to the provided argument if the host made a valid selection or 0xF if the
selected function was invalid.
−
Maximum current consumption under the selected functions. If one of the
selected functions was strong the return value will be 0.
Check Function
Switch Function
CMD6
Res
Status Data
Status Data
Card internal
execution
Card internal
execution
CMD
DAT
CMD6
Res
CMD
DAT
Switched Function
Current Function
(Mode=0)
(Mode=1)
Function change timing:
within 8 clocks