>Thanks a great deal to all who gave me suggestions.  I changed the unused
>PIC I/O from outputs to inputs, and tied them all to ground.  The circuit
>works like a champ!  I tried to re-create the problem, but I had no
>"success" (prior, the problem was easily reproducible).
>
>FYI, I know I forgot to mention some things about the HW design.  All
>along, my mag switch, when open, is pulled up to 5V and closes to ground.
>The switch is not debounced, though I will implement a design utilizing an
>R/S flip-flop.


You don't need any hardware, you can debounce by software.

Gabriel


>
>Thanks again to all who responded!  I hope you all will be as much help in
>the future.
>
>Best regards,
>
>--John
>
>
>
>
>
>Quentin <qsc@ICON.CO.ZA> on 02/17/99 03:11:14 PM
>
>Please respond to pic microcontroller discussion list
>      <PICLIST@MITVMA.MIT.EDU>
>
>To:   PICLIST@MITVMA.MIT.EDU
>cc:    (bcc: John Esposito/gg/DadeInt)
>Subject:  Re: Hardware or software problem???
>
>
>
>
>Meet PICcy, your friendly ghost. :)
>
>I know you said you configured all unused pins as outputs, but this
>still looks very much like you getting interference through a floating
>input. Double check that. Also check RB4.
>Could be your breadboard is having a bad connection.
>Do you have a pullup/pulldown resistor on your switch input?
>As a test, make all unused pins as input and connect them to ground.
>connect the case of your Xtal to ground.
>And, I don't think it is your problem, but you don't need the 74HC04 to
>drive the LED, you can do that direct from the PIC pin via a 680 ohm
>resistor.
>
>Just a few things I can think of.
>Quentin