56F84789 RAM problem

[bobc]

Hi there,

We have encountered a strange issue on certain 56F84789 chips. The last 4KW of RAM (0x3000-0x3FFF) is unusable. On read, each word is 0xFFFF. Attempting to write a word in that range has no effect.

We only find this problem with two specific date codes so far, all other date codes appear normal.

Some questions:

1) Is this a silicon fault?

2) Are there any configuration bits that could stop part of RAM not working as expected?

3) Has anyone seen this type of problem?

Cheers

[johnlwinters]

Hi,

It could be a silicon fault.

I have not heard of this issue.

Please, what are the data codes where the issue exists?

What percent of the units of this data code have the issue?

How many units have this issue?

What stage is the project for which these units are stocked in?

You many want to contact your local Freescale FAE for support on this issue as a next step.

[bobc]

Hi John,

We are at pre-production stage so there are a limited number of PCBs built. I've been looking through every board and it appears that the following two date codes exhibit the problem :

QQAG1425H

QQAG1425J

with 100% rate, but there are only 6 chips with these date codes. All other date codes appear to be OK. We have several boards build into prototypes, I haven't been able to check those.

My colleague has raised an SR and contacted our local FAE, I will leave it with them and update if we get any news.

Regards