I have a problem. I am programming a PIC.
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hehe.. known trouble source, indeed :)
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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.
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11111100+00000011=0xff --> 0xff-your current data=your desired data.
 
Only useful if your data is always less than D'126'...