In a message dated 5/3/99 2:19:31 PM Pacific Daylight Time,
andreas.m@TELIA.COM writes:

<< Hello all!

 I have a problem. I am programming a PIC. In the program I load a value from
portb to the register TANKOD. The value from portb tell me wich button that
is pressed down on a keypad. If button 3 is pressed, 3 will be the value of
portb.

 My problem is that the keypad use "negative logic" or something like that. A
0 is a 1 and a 1 is a 0. So i want to invert the register.

 11111100    =>    00000011


 Any Idea how I can do this in a easy way.


 Tnx    /Andreas Magnusson
  >>
Hi Andreas,

How about:


        xorlw   b'11111111'                             ;exclusive OR W with
all 1's


W register should contain the value obtained from port B.
when finished, the W reg will be inverted.


Dave Duley