A simple 8-bit arithmetic logical unit.

The following commands are implemented:

Logic Operations:
[0] 000: OR
[1] 001: NAND
[2] 010:NOR
[3] 011: AND
Arithmetic Operations:
[4] 100: ADD
[5] 101: SUB

The two's complement for subtraction is implemented with a NOT Gate and an adder (which simply adds 1 to the negated input).