DT Interupts PortA or PortB?

[Charles Linquis]

There is no hardware support for interrupts on PORTA. But that doesn't mean you can't use interrupts to do what you want.
A good way is to determine the shortest switch closure that you must detect (50mSec?). Then set up a timer that interrupts
at that rate. You mention that you are already using DT-INTs for timing, if you are using a timer for that, just "piggyback" on
that INT. If you aren't, just set up another timer (I like TMR3 for such things). The interrupt rate must be as fast as the shortest
switch closure you want to be able to detect. You ISR could be something like -

SwitchInt:  ; The ISR

IF PORTA.5 = 0 THEN
    IF SwitchHasBeenClosed = 0 then
            Pause 10;    Debounce
         IF PORTA.5 = 0 then   ; Still low?
            SwitchHasBeenClosed = 1
            SwitchHasBeenClosedFlag = 1
         ENDIF
     ENDIF
ELSE
    IF SwitchHasBeenClosedFlag = 1 then
         Pause 10    ; Debounce time
         IF PORTA.5 = 1 then  ; Still high?
             SwitchHasBeenClosedFlag = 0
             SwitchHasBeenClosedThenOpened = 1
         ENDIF
     ENDIF
 ENDIF
          
      

@ INT_RETURN

; You can clear the flags as appropriate such that you don't perform multiple operations with one switch push.