Digital System Design

Combinational logic circuits are circuits whose outputs depend only on the present value of their inputs. The lecture on “Combinational Logic Design” introduced you to some of the common combinational logic circuits.
For your second project, you are required to Design, Implement, and Test an 8-bit Arithmetic Logic Unit or ALU. By using VHDL (Use block diagram shown below

Recommended Design Procedure:
1. Find the number of input variables and the number of required output variables. Assign them meaningful names.
2. Create a truth table that defines a relationship between inputs and outputs.
3. List the operations (Choose any Five Arithmetic and Logic Functions, in which Shifting and Comparator should be included) that you will be implementing – the more the better 4. Draw the logic diagram.
5. Implement your design using VHDL
6. Test your design by creating a test bench

Give a brief discussion of the theory of operation, including schematics and equation used, etc. This is of importance for the design oriented labs and mini-projects. You should also explain the schematics involved in your design.

4. Experimental results: (70 pts including the section on “Theory of Operation”) • Brief description of the lab experiment.
• Schematics of the circuit (from Xilinx schematic entry tool). Put your name and date on each page.
• Simulated waveform.
• Discussion of the results indicating that the circuit functions properly. It is not good enough to just give the simulated waveform. It is up to you to show that this waveform corresponds to what you expect (do not say “the simulation shows that the circuit works properly”). You need to make it clear to the reader that the circuit works properly! One convenient way is to use some of the entries in the truth table in your test bench, indicating that for each entry/input the corresponding values/outputs given by the logic simulator correspond to what is displayed in the table.