I am working on a little project using the 12C508A.  It is a garage door
warming system.  The Pic is connected to a buzzer and two LEDs (GPIO 2), one
red(GPIO 0) and one green(GPIO 1).  I want use GPIO 3/MCLR/Vpp for
detection.  Here is a short program I wrote:

start:          org     0x00
                movlw   0x38
                tris    gpio            ;set gpio 0, 1, 2 as input and the
rest as output
                movlw   0x3f
                option                  ;enable weak pullup and wake on pin
change, bit 6 and 7
loop:           btfsc   gpio, 3         ;check and see if gpio 3 is low
                goto    loop            ;if not check again
                call    buzzer          ;make the buzzer buzz
                goto    start

When I program the PIC I use LP crystal, internal MCLR and no watchdog.

The problem I have is gpio 3 is acting as an input pin.  I don't know how to
debug it because the ICE doesn't emulate that pin.

Please help.

Ben

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