RE: [microblaze-uclinux] Problem with 2nd stage bootloader (u-boot)

["Kevin Somervill" <kevin.m.somervill@xxxxxxxx>]

If I may interject...

| From: owner-microblaze-uclinux@xxxxxxxxxxxxxx 
| [mailto:owner-microblaze-uclinux@xxxxxxxxxxxxxx] On Behalf Of 
| John Williams


| >>If you read from the address (using u-boot's memory read 
| >>command or xmd) do you get 0xffffffff at flash addresses (ie 
| >>blank flash data)?
| > This is what I get:
| > 
| > U-Boot> md 0x28000000
| > 28000000: ffff0008 aa99ffff 2000ffff 3000ffff    ........ ...0...
| > 28000010: 0000ffff 2000ffff 2000ffff 3001ffff    .... ... ...0...
| > 28000020: 0004ffff 3001ffff 0167ffff 3000ffff    ....0....g..0...
| > 28000030: 0000ffff 2000ffff 3000ffff 0000ffff    .... ...0.......
| > 28000040: 3000ffff 0000ffff 2000ffff 2000ffff    0....... ... ...
| > 28000050: 2000ffff 2000ffff 2000ffff 2000ffff     ... ... ... ...

This is not what you would read from a failed device.  Two things stick out:
1. the first read has the half-words reversed with the others which is
indicative some sort of timing problem (goofed up parameters in the MHS or
bad constraints in the UCF, most likely the former).

2. for a device failure, I would expect the FFFF to be random junk and not
stuck high.

I'm not familiar with your hardware, so I have the following questions:
1. Have you ever gotten a reference design to reliably access the "failing"
device? (Outside of attempts at uClinux)

2. What are the differences between what you have and the reference design?

3. Are the address lines shared between the two flash devices?

4. Can you reliably access the "working device"?

5. What is different between the connectivity of two devices (besides one
doesn't work)?  If nothing, maybe that's the problem?

6. Do you have pull-ups on the DQ lines?  Switch them to pull-downs and see
if the FFFF got to 0.  This might indicate an failed OE line.

A few points to ponder as you sort out your hw.

Happy hunting.
./ks

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