|Can anybody tell me how to do a 2's complement of hex# stored in the w
|register.  Thanks

On the 14-bit parts, you may use 'sublw 0'.  This is, obviously, the
fastest way to do it.

On the 12-bit parts, you may use:

        addwf   reg,w
   subwf   reg,w

If 'reg' were to change between the two instructions, the value in
W would be corrupted.  Given that none of the 12-bit parts support
interrupts, though, you should be okay provided 'reg' is not an I/O
port or similar register.

Hmm... and here I thought the fastest way to increment W without a
spare register was:

        subwf   reg,w
   incf    reg,f
   subwf   reg,w
   decf    reg,f

but there's a three-cycle way:

   xorlw   255
   addwf   reg,w
   subwf   reg,w

Cute, eh?