[U-Boot-Users] Not primarily u-boot related problem with Flash-RAM

[Peter Asemann]

Hi there!

I've a problem that is not really u-boot specific; in fact it rather 
stands in my way to be able to use the U-Boot at all. I'm sorry for the 
off-topic post, but as this list's topic is the one most close to 
"bringing up boards" I hope you can help me a bit though:

I have a prototype board which has an MPC875 with 4 AM29LV320DB flash 
chips on the bus (there also are 2 SDRAMs and an FPGA on the bus).

The board had a design flaw which made some buffers/level converters 
which should convert the bus signal level to the signal level of a 
PCMCIA adapter kind of burn out or at least disturb bus operations on 
the data- as well as address-bus.

We've therefore removed the buffers/level converters, and now the busses 
  work, as we can see with a test program running on the FPGA (which 
monitors the busses and draws block graphics of the last non-identical 
32 bus states on a VGA display). That means, the MPC and the FPGA seem 
to have survived what ever was wrong with the busses.

But though the busses seem to be okay now, the flash doesn't react to 
the ident command sequence as it should, though I tried very defensive 
clocking and stuff.
So the question is if you know typical mistakes which can cause 
accessing flash to fail, or if you know that flash chips are well known 
to go into pieces if there is something wrong with the busses connected 
to them. Any hint will be appreciated.

Thanks for reading,

Peter Asemann