Mike,

The code I have is very small (some few instructions for testing) and there is an infinite loop which does something like this:

LOOP: ...
MOV P0, R1
MOV P1, R1
MOV P2, R1
MOV P3, R1
...
(code that increments R1 and inserts a delay)
...
LJMP LOOP

I know the code is being executed because I can see the output in P1 and P3, but P0 and P2 never change.

I know the micro is Ok since I have tried with different chips (same model though) and the result is exactly the same.

Regards,
Mikel