SDI Technologies SDIO Card User Manual

 

 

 

©Copyright 2000-2007 SD Card Association  

 4 

 

 
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. 
 

 

 

Idle State

CMD0 + CS
asserted (0)

SPI Mode Idle

State

Inactive State

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

Busy

CMD1

Card is MMC

Response

No

Response

SDIO card is

Rejected

Invalid

Cmd

CMD58

(optional)

Busy

Invalid

Cmd

CMD0