Mark C.

Do they appear in different places from run to run, or are they always in the same locations? Do you have the original binary / are they definitely not intentional / "supposed to be there"?

Also, is it always 8 of 64 bytes that are 0xFF? and repeated throughout?

Is that just a data segment? It doesn't look like thumb code, do the 0xffs repeat across the extract?

All the way across.

Dodgy interface or cables ?

nah - it's way too regular an 'error' for that :-/

I'd start with GND issues, next double check the power supply and make sure it's sufficient, next maybe lower the speed, and lastly throw a logic analyzer on it and check the commands it's using because the 0xff blocks seem to be consistently spaced.

No matter which cmds I send I get the same output from these blocks no matter where they are requested... Even at very slow speeds and as close to manual as I can with OpenOCD. No ground issues, minimal noise, and the same setup pulls firmware fine at full speed from test rig

Ive only seen this once and it was a ground issue

Also to not, i had alot more FF’s that what you have there