Alan Smith wrote:

> I am relatively new at programming PICS and I have encountered my
> first uncrackable bug!

  No problems!

> My problem is: I can't seem to control IO pin 10 in a certain region
> of code.  The instruction I am using is as follows: bcf portB,4.

  Rule No.1  Don't use BSF/ BCF/ ANDWF/ COMF/ ORWF /IORWF or any similar
instruction with the I/O register as destination, on a PORT register.
Always set it using the MOVLW mask; MOVWF PORTx sequence you used for
the OPTION and TRIS set-ups.  If necessary, keep a "shadow" register
with the settings you want on the outputs, modify that one bit at a time
and copy to teh PORT.

> Pin 10 is only connected to a 0.1uF cap which goes to 0v.

  Why on earth?  A 0.1µF capacitor at microcontroller execution speeds
appears as a SHORT CIRCUIT.  Why would you do that?  Also, how would you
know if/ when the pin state changed with this connected?

  Put that cap across pin 5 & pin 14 instead!

  Rule No.2  Don't connect large capacitors across I/O pins.

  Rule No.1+2  Don't *ever* use BSF/ BCF etc... instructions on port
pins connected to capacitors.  These are "Read-Modify-Write"
instructions which base their estimate of the pin states not
specifically defined in the instruction, on what the pin state is, *not*
what you last wrote in the register.
-- 
  Cheers,
        Paul B.