On Wed, 24 Jun 1998 13:14:41 -0500 "Jonathan M. Newport"
<jnewport@MAIL.ORION.ORG> writes:

>continuous loop like:
>
>circle  goto    circle
>
>waiting for an interupt.  when the isr is finished and I use the
>retfie
>command, will it increment the program counter to execute the
>instruction
>after this one?

No. When the interrupt is done, the program will continue in the endless
loop.

 or if it doesn't is there a way that I can increment
>the
>program counter myself?

You can't change the program counter on the stack (Even if you could, it
wouldn't be a very good practice since you'd also have to be sure that it
was the endless loop that was interrupted).  The most flexible way to do
it is to have the ISR set a flag, then test the flag in the main program:

(flags is a byte in RAM, and isrdone is a constant from 0 to 7 indicating
the function of that bit in flags)

[In the ISR]
....
        bsf     flags,isrdone   ;Tell main program the int. has
occurred.
...
        retfie

[In the main program]
        bcf     flags,0         ;Interrupt hasn't occurred.
[Enable interrupts, etc.]
waitint btfss   flags,isrdone   ;Skip if flag is set
        goto    waitint         ;Otherwise keep waiting
;Here after interrupt.

This technique is very flexible.  For example, if the ISR is collecting
data being sent serially, it might not set the flag until after a whole
byte has been received.  The main program would then wait until the byte
is complete.

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