Moshe Fish wrote:
>
> I have tried to take the same code (to which I added a GIE) and delete all
 parts
>  of the code which relate to port B and the other ports leaving only Port A
>  setup and the test. The code works perfectly and I can see it on the scope
>  (which by the way is a Tektronix digital scope).

Hard to go wrong there...

>                                          This leads me to believe at
>  this stage that somewhere in the portB setup there is something that is
>  affecting port A. By the way the simulator (I do not have an emulator) shows
 it
>  working fine on the code with the portB interrupts.

Here are a few more ideas. 1) Are you certain that your pic include
file P16C65.INC is O.K.? Specifically, it's possible that your PORT B
 definitions
may be fubarred. 2) Have you tried another target PIC16C65? Maybe you have a bad
chip. 3) Where in your code did you enable GIE? Since the interrupt routine does
not save the STATUS register and reinitialize it for its on use, there's a
 chance
that RP0 is in the wrong state when the interrupt occurs. Consequently, your
 write
to PORTB would instead be going to TRISB; ditto for the PORTA write. This could
change the PORTB inputs to outputs!


> I still remain mystified although I am sure that when I discover what
> it is I will fell like an idiot..............->feel? or fail?

That's O.K. all idiots eventually fell (fail). However, I'm sure your no idiot!

Scott