Hi all
Sorry, I didn't give enough info when I first posted the question.
The chip is an F876.
I can't use capture ports. One - I need one for a PWM output, and two -
the times I'm measuring are way too long, sometimes two or three
seconds.  Actually it deosn't have to be a 'time' as such, like in
seconds, rather just a number which represents a period.  Hence I just
count 'periods' which are derived from timer interrupts.
I'm in the proces now of trying the RB0 interrupt, with diodes to two
other inputs, which seems to be OK.  On interrupt, first thing is
disable gie.  Then poll each of the two inputs for the signal, then act
on which one it is, then re-enable gie.  Yes... I might get a conflict
now and again, like the second interrupt comes along while I'm servicing
the first one, but with the slow periods I'm dealing with, it most
likley won't happen often, and if it does, it'll only be a glitch which
won't be a problem either.
However, after all that, I must seek more knowledge about capture and
compare, as it may be usefull later on, and I know absolutely nothing
about the function - in fact, I'm not sure what it actually means - yet!
Regards
Howard

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