Hello all,
I am hoping someone can help with a problem I am having developing a
winxp driver for an SDIO device.
I can do pretty much everything I want with the driver but I have one
problem.
In order to test the SDIO 1-bit mode of of my device I need to instruct
the bus driver to conduct SDCMD_IO_RW_EXTENDED operations (CMD53) in
1-bit mode as opposed to 4-bit mode. (which seems to be the default.
I am able to switch the SDIO card from 4-bit to 1- bit by writing 0x40
to CCCR offset 0x7.
However when I perform subsequent CMD53 operations I discover realise
that the host side (understandably) hasn't noticed that we now want to
use only one bit but not 4.
By using a scope I can verify that the the following operations are
still conducted in 4 bit mode however now the card does not understand
because it thinks we have switched to 1-bit mode.
I have searched the MS SD api looking for a way to tell the host that
we have switched to 1 bit mode but I can find no such function.
Is it possible that XP detects that the card is capable of 4 bit
operation and simply doesn't have the option to switch back to 1 bit
mode?
This makes it very difficult to verify 1 bit support on the device
under development.
Any help on this matter would be greatly appreciated.
Best Regards,
Dave
