Roberts II, Charles K. wrote :

> I was taught the following convention when it comes to ISR's
>
> I have an ISR which monitors the Interrupt bits,

Your ISR doesn't "monitor" anything (normaly). That's
a "polling" routine and not an "interrupt" driven routine.

> So the ISR is only called when an interrupt signal is received
> by the micro and causes it to start reading code at specified
> at the interrupt vector.

This is not what you said above, or ?
(But is correct.)

Now, what your ISR has to do first is *now* to check the
interrupt bits to find out *which* interrupt event trigged it
and then probably jump to some specific "handler" for each event.

Note also that many architectures (not the PICmicro) has "soft-interrupts",
such as an specific interrupt vector for "illegal instruction" or "divide by zero"
or whatever. Those are internaly generated interrupts that has nothing to
do with any external event, but from the ISR's standpoint work the same way.

Regards
Jan-Erik.
(Comming from the PDP11/RSX-11M and OpenVMS VAX/Alpha world...)
(Well, still beeing in the OpenVMS world, since that is my main
occupation as an consultant today...)

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