Hi Robert,

a couple of things I might have done differently, just out of personal
preference not to get bogged down in unnecessary problems

I generally wouldn't do a goto $ + 3. goto +/- 1 or bra +/- 2 I'm
OK with, but further than that I'd use a label, eg goto DecTmrE.
Without a label to jump to, later code editing can easily miss the
destination of the goto or bra

xorwf could be a source of read-modify-write issues on those PICs
without an output latch

movlw LED_MASK ; Sound a tone to remind the user that
xorwf GPIO,f ; the door is open.

The xorwf reads the port and then writes the modified value back to
it. In some situations this could cause unexpected pin values, leading
to much head scratching and profane language

Modifying a shadow register is safer. Something like

movfw gpio  ;read port
movwf shadow  ;into shadow register

movlw led_mask  ;modify shadow register
xorwf shadow,w

movwf gpio  ;write it to port

http://www.piclist.com/techref/readmodwrite.htm

Joe
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