AVR-Chat

Paging any compact flash experts out there...

I designed a unit some time ago that plays WAV files off a compact flash
card. It worked fine. Then recently some CF cards have come along
(varying manufacturers) which don't work properly. The WAV file is
corrupted on playback.

The unit has a parallel DAC to output the audio, and I have one ~WR line
which goes to both the DAC and the CF card. Then I have a separate ~CS
lines for the DAC and the CF card. A shared databus goes to both the DAC
and the CF card.

These CF cards which don't work appear to ignore the ~CS line - if the
~WR line is taken low with the ~CS line high (Inactive), such as when
I'm writing to the DAC, then the card still thinks it's being written
to. There's no glitches on the ~CS line at all. (there's actually 2 ~CS
lines on a CF card, the other is firmly tied to VCC)

Searching the web reveals a few other people who have found this
problem, but nobody with any answers as to why. The latest Compact Flash
spec says nothing about it. Anyone else know or have any ideas?

-- 
Tim Mitchell
tim@sabretechnology.co.uk
http://www.sabretechnology.co.uk