Hi,
You don't want to use the XOR operator, you want the ^ (bitwise XOR).
Code:
A VAR BYTE
B VAR BYTE
C VAR BYTE

HSEROUT["Start",13]
A = 0 : B = 45
GOSUB Display

A = 255 : B = 45
GOSUB Display

PAUSE 10
END

Display:
C = A ^ B
HSEROUT[DEC A, " ^ ", DEC B , " = ", DEC C,13]
RETURN
Gives
Code:
Start
0 ^ 45 = 45
255 ^ 45 = 210
If it doesn't work at your end, please post the code.

/Henrik.