Stephen said:
"While PIC may be marketed as such, Scenix is the only truly
deterministic 8-bit architecture. Determinism not only applies to fixed
cycle length for a given instruction, but also a fixed interrupt response
time. While PIC may have the former, it's architecture has a variable
interrupt response, depending on what executing instruction was
interrupted."

I don't think this is strictly true. I am pretty certain some (all?) PICs
are fully deterministic on interrupt response for external interrupts. They
simply delay an interrupt that occurs during a single cycle instruction by
one extra cycle relative to one that occurs during a two cycle instruction.

For internal interrupts it doesn't happen that way, but you can sometimes
dejitter the interrupt by looking at, for example, the timer register. I do
this last on an 18C part to get a zero jitter interrupt based on timer 2.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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