Re: Plea for MMC spec owners

[Pierre Ossman <drzeus-list@drzeus.cx>]

Khasim, Syed wrote:
> Hi Pierre,
>
> Regarding 2GB, the MMC specification doesn't state any thing clearly as
> the SD spec does.
>
>   

That's too bad as I was hoping we could avoid guesswork. :-/

> As per my understanding, MMC (of all sizes) by default should be set to
> operate in 512B (mandatory). This is true for both read and write. With
> this default setup, I feel MMC card (<=2GB) should work as is with BLEN
> set to 512.
>   

That is my feeling as well. But it would have been nice to back it up
with an official spec.

> However, if the size of MMC is greater than 2GB then it switches to
> sector access mode (<=2GB operates in byte access) and we are supposed
> to read from EXT_CSD register for getting the density of card. I was
> wondering if for some reason on some of the cards it's switching to this
> mode and therefore it's not consistent across all the 2GB MMCs.
>
>   

This voodoo you speak of is rather unknown to us since we lack a real
MMC4 spec. ;-)

Rgds
Pierre