Did you know that most AVR chips have a type of hardware exclusive OR (XOR) option when it comes to the logic levels of the output pins? If you look in the datasheet (the image above is a ...

As an example, let’s consider the AND gate (the others are OR, NOT, NAND, NOR, XOR and ... The output of the gate, A.B, depends on the two inputs according to the truth table at the right.