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

[richard at uclinux.net]

Hi over there...

> 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.


So you say that all 4 flash chips don't work anymore?
Can you access the flash through FPGA?

I would just do:

- grab jtag tools from openwince project
- add busdriver for mpc875 according to bsdl file and your hardware
- try to access flash manually...

Good thing about jtag tools is that you can also set individual
pins or see individual pin states...


rick