CS 245 Design a Simple ALU 

Purpose:

Become familiar with the design process of common ALU components.

Procedure:

1.  Design the 8-it adder.

            Use the 1-Bit Full Adder we designed in class as the basis of your 8-bit design.
            Cascade 8 Full Adders together.
            Simulate, and verify, your design by adding several 8-bit binary numbers.

2.  Design the 8-bit ANDer.

            This is done by simply putting 8 AND gates in parallel.

Questions:

How could you modify your 8-bit adder to make it subtract as well?

What are some of the ways you could switch easily between the operations (without any re-wiring!)?  HINT: Think of a way you could simply toggle a control bit that would make it add or subtract without having to manually reconfigure anything.  (Two's complement is very easy to implement with this adder.)