> The compliance against standards varies considerably across
> the market.  My guess is you've found a bug in the firmware, a
> corner case that is exercised by your pattern of access, but is
> not tested by the device manufacturer or firmware vendor.

I probably shouldn't expect them to, as SPI seems more of a
courtesy vs the licensed 4-bit i/f encountered commercially

> - switch to a pattern of access that is known to work

That's partly the problem. As mentioned, I have a scheme that's
very reliable with one type of card which doesn't work with others.

> Perhaps the card wants a supply voltage change; some SDHC
> or SDXC cards require 1.8 V at higher transfer speeds.

I have tinkered with the s/w flow quite a bit, but not tried changing
to 1.8V. In the PC card reader which I use to transfer files to the
cards Vdd is 3.4V

Joe



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