I am familure with this requirement but hadn't thought about how to do it
on a PIC.  Maybe you could throw another PIC at the problem.  The second
PIC reads the first PIC's ROM and does the check sum.  If needed, the first
PIC could also check the 2nd PIC's code.  Kind of a round about way of
doing it but it might work.  The 2nd PIC might be the cheapest approach.

Norm

At 08:19 AM 3/14/97 +0000, you wrote:
>I want to verify the program at runtime every time
>it is powered up.
>
>Som aplications regarding human safety requires that
>the processor checks itself for a corrupt program,
>checks that every used instruction is working ok and
>checks that every used ram register is working before
>it can go on with it's safety part of the program.
>
>The instruction- and ram-checking is ok but since
>I can't read the memory with the instructions
>(Harvard Architecture) I can't do any checksum
>test.
>