4-bit SD Card mode

Neil Bradley nb at synthcom.com
Thu Jun 7 07:54:29 UTC 2007

> I think lot of you know the message 'Setting controller bus width to 1' in
> conjunction with AT91 SD Card interfaces. I'd like to suggest to disable
> this message in src/arm/at91/at91_mci.c for two reasons: 1) it occurs
> excessively and 2) there is no useful information content with this
> message. Since it is improbable that the driver ever supports the 4-bit
> mode we also don't need to be informed whether we use 1-bit or 4-bit mode.
> It is improbable (unless somebody is already working on it) because the
> 4-bit mode requires either polling or a very special interrupt handling
> that is not covered by the publicly available simplified SD Card
> specifications.

I've done SD drivers, both 1 and 4 bit, DMA and programmed I/O, on the 
PXA270, Atmel SAM7, Atmel SAM9, and Freescale MX31 CPUs. How may I be of 


C. Neil Bradley - KE7IXP - The one eyed man in the land of the blind is not
                            king. He's a prisoner.

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