SDI Technologies SDIO Card Manuel D’Utilisation
©Copyright 2000-2007 SD Card Association
SDIO Simplified Specification Version 2.00
4
3. SDIO
Card
Initialization
3.1
Differences in I/O card Initialization
A requirement for the SDIO specification is that an SDIO card shall not cause non-I/O aware hosts to fail when
inserted. In order to prevent operation of I/O functions in non-I/O aware hosts, a change to the SD card
identification mode flowchart is needed. A new command (IO_SEND_OP_COND, CMD5) is added to replace
the ACMD41 for SDIO initialization by I/O aware hosts (see 3.2).
After reset or power-up, all I/O functions on the card are disabled and the I/O portion of the card shall not
execute any operation except CMD5 or CMD0 with CS=low. If there is SD memory installed on the card (also
called a combo card), that memory shall respond normally to all normal mandatory memory commands.
An I/O only card shall not respond to the ACMD41 and thus appear initially as an MMC card (See appendix B.1
for information on the MMC specification). The I/O only card shall also not respond to the CMD1 used to initialize
the MMC cards and appear as a non-responsive card. The host then gives up and disables this card. Thus, the
non-aware host receives no response from an I/O only card and force it to the inactive state. The operation of an
I/O card with a non-I/O aware host is shown in Figure 3-1 Note that the solid lines are the actual paths taken
while the dashed lines are not executed.
Figure 3-1 SDIO response to non-I/O aware initialization
Idle State
CMD0 + CS
asserted (0)
asserted (0)
SPI Mode Idle
State
Inactive State
SPI
SD
Reset
SDIO card is
Rejected
No
Response
Response
No
Response
Normal SPI
memory operation
ACMD41
(arg = 00)
ACMD41
arg = working
voltage
Response
Normal SD
memory operation
CMD1 or
ACMD41
ACMD41
Busy
CMD1
Card is MMC
Response
No
Response
SDIO card is
Rejected
Invalid
Cmd
CMD58
(optional)
Busy
Invalid
Cmd
CMD0