Hi I've been struggling with a problem for a while now so I thought that
maybe somebody out there may have seen this one before.

Basically I'm seeing my RBIE/RBIF (Int on port b change) interrupt routine
being called even though the RBIE (enable flag) is clear. Basically my int
handler looks like this.....

InterruptVector
     push                 ; Always save registers etc
CheckInterrupt
     btfsc INTCON, RBIF   ; Is it a PORTB int ?
     goto ServicePORTB    ; yes so go do it
...
...
ServicePORTB
     btfss INTCON, RBIE   ; Test to see if we have ints enabled
     nop                  ; This should never be executed!
     bcf INTCON, RBIE     ; turn off further ints
     movf PORTB, W        ; read port to reset it
     bcf INTCON, RBIF     ; say we have seen this change
....
....

EndInterrupt
     pop                  ; restore things
     retfie               ; return and re-enable ints

Ok what I see happening is that if I set a breakpoint on the nop just after
the ServicePORTB label. Then From time to time I get a break. This was
really screwing up the rest of my interrupt routine (easy to fix just
replace the nop with a goto to skip the int routine). What seems to happen
is that the int routine gets called once with RBIE enabled - OK, then
immediately again with RBIE now disabled - not so good. So my question is -
should this happen? If so why? BTW the interrupt gets enabled (RBIE set in
the main body of the code

The environment I'm using is an ICEPIC emulator with the
16C71/16C7110/16C711 module installed. The signal that I'm feeding into a
single pin on PORTB is a rather noisy standard Radio Control pulse (+ve
pulse of length 1-2mS repeated every 20mS).

Thanks

Andy