CS 150 Design a Simple ALU 

Purpose:

Become familiar with the design process of common ALU components.

Procedure:

1.  Design the 4-bit adder.

            Use the 1-Bit Full Adder we designed in class as the basis of your 4-bit design.
            Cascade 4 Full Adders together.
            Simulate, and verify, your design by adding several 4-bit binary numbers.

2.  Modify your 4-bit adder to make it subtract as well. 

            HINT: A MUX could be used on the "B" input of each adder to select between B and B'.  Think of a way you could simply toggle a control bit that would make it add or subtract without having to manually reconfigure anything.

3.  Design the 4-bit ANDer.

            This is done by simply putting 4 AND gates in parallel

Questions:

What are some of the ways you could switch easily between the operations (add, subtract, AND) without any re-wiring?