Greetings!

I'd appreciate a reminder of something which I know has been discussed
before on the PICLIST, but which I have not so far found in the various
PIC FAQs on the WWW.

I wish to put a 16C84 into sleep mode in a low-power application until
either of two Port B inputs receives a "low" pulse of about 1 second
duration from an external device.  I believe that it should be possible
to use the Port B (RB4-7) "wake-up on change" facility to achieve this,
but I recall that there are some potential pitfalls to avoid.

I enclose a snippet of code which forms the main program loop:

INIT
        MOVLW   B'01010000'     ; Set RB4 and RB6 to be inputs
        TRIS    PORTB           ; .. outputs are "don't cares"
        MOVLW   B'00001000'     ; Configure wake-up from sleep
        MOVWF   INTCON          ; .. on RB4-7 (no interrupts)
LOOP
        BCF     INTCON,RBIF     ; Forget any previous activity
        COMF    PORTB,W         ; Get inverted port bits
        ANDLW   B'01010000'     ; Mask off RB4 and RB6
        BTFSS   STATUS,Z        ; If either is active
         GOTO   PULSE_RCVD      ; .. deal with it
        SLEEP                   ; Snooze until RB4-7 change
        GOTO    LOOP            ; Process the change

Note that my PULSE_RCVD routine completes in much less than one second
and administers a reset pulse to the external device to release the
appropriate (RB4 or RB6) input before it returns to "LOOP".

It is crucial that no input pulses are missed.  Will the above code
achieve this?

Thanks in advance for any assistance.
--
Ian Chapman