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

[Andrew Dyer <amdyer@gmail.com>]

> Are you sure that the flashes ever worked?  One  typical  problem  is
> that  it  seems quite natural to connect the D0 pin of the flash chip
> to the D0 pin of the data bus, etc. - which is wrong, since  for  the
> flash chip D0 is the LSB, but on PowerPC bit 0 is the MSB...
> 
> Can you access (read, erase,  program)  the  flashes  through  a  BDM
> debugger?
> 

I don't know the particular CPU, but along the same lines (learn from
my mistakes!):

1) did you hook the flash up in the correct mode (8 vs. 16 bit) 

2) did you hook CPU addresses to flash addresses correctly?  This will
depend on the flash mode setting and the CPU.  At least one part I've
used (Toshiba TX4925) changes the
connections between internal and external address busses based on the programmed
width of the chip select - i.e for a 32-bit wide select it will
connect the A2 out of the MMU to
the external A0, for a 16-bit wide it connects A1 out of the MMU to
external A0, etc.

3) In s/w when doing the ID cycle are you writing to the correct
address in CPU space to generate the right pattern on the physical
lines hooked to the flash to make it recognize the ID commands?

and as a reminder of things one ought to be doing, these are a good
set of rules:
http://www.debuggingrules.com/debuggingrules.pdf (for more explanation
on these check out the book "Debugging" by Dave Agans - no
affiliation, yada, yada)


-- 
Hardware, n.:
        The parts of a computer system that can be kicked.