Debugging a TMS320

[don.r]

I have an HP MSO that has an intermittent failing trace issue. Since both the digital and analog channels fail at the same time and since it passes all RAM/ROM tests and is otherwise operational, I am beginning to suspect the TMS320C50 DSP. I can't find a CLIP or schematic for this scope so I am assuming the DSP is the common signal point before the CPU.

Is there a standard approach to debugging these besides obvious stuff like monitor clock pins, supply pins, etc? Unfortunately the scope is my only logic analyzer so monitoring 4 data lines on my Tek 2245 is my maximum capability.

EDIT: Nevermind. TMS320 appears operational. Problem is with trigger circuit... probably trigger ASIC.