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Thread: Simultaneous Interrupts
www.piclist.com/techref/microchip/ints.htm?key=interrupt
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face BY : Don Hyde email (remove spam text)



A PIC multithread OS can be done if the individual threads are not allowed
to do any call's and return's.  For each thread, you need to store the same
stuff that the interrupts save (w, status, PCLATH, etc.)  Since most PIC's
have no way of reading the stack (except for the 18Cxxx), there is no way
for the OS to save the call/return history of individual tasks.  This
limitation makes PIC multitasking, well..., pretty much useless.

Much the same end effect can often be accomplished by writing code that
implements multiple state machines, in which case you may be able to get by
with as little as one byte of state per machine.  You might even manage to
implement something resembling preemptibility.

> {Original Message removed}
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