ENGR338 Lab Spring 2021
Lab 9: Design a Simple 8-bit ALU in ElectricVLSI
Name: Audra Benally

Email: albenally1@fortlewis.edu

1. Title: Design a Simple 8-bit ALU in ElectricVLSI

2. Introduction: In this lab we combined the previous 8bit components to make a simple 8 bit ALU. The ALU was created in schematic and layout cells and has been tested in several simulations.

3. Materials and Methods:

                 - Computer
                 - Computer Mouse
                 - LTSpice Software
                 - ElectricVLSI Software
             For this lab,
we created a simple 8bit ALU. Most of the components were already created in past labs so the only one I had to make for this lab was the 8bit inverter. After I had finished I started making the layout since I knew this would take the longest time. I drew a rough idea of how I wanted to layout the schematic then I got to work. The layout was tricky but I was able to get it to pass DRC, NCC, and well checks. Once the ALU was finished it was tested in various simulations shown in the figures 4-7.

4. Results:

             Figure 1. 8bit ALU schematic made from the 8bit components made this semester.

             Figure 2. 8bit ALU layout. A[0:7] and B[0:7] inputs are on the left. S0 and S1 pins are on the top. S[0:7] and Co[7] outputs are on the right.

             Figure 3. DRC, NCC and well checks for the ALU.
             Figure 4. S0=0 & S1=0: AND logic simulation.

             Figure 5. S0=1 & S1=0: OR logic simulation.

             Figure 6. S0=0 & S1=1: Addition simulation.

             Figure 7. S0=1 & S1=1: Subtraction simulation.

5. Discussion
    This lab was very interesting. It was much more complicated so unsurprisingly I had much more issues than usual. I had mixed up the A and B inputs for the FA at first but quickly remedied that once I did a thorough check. I had a lot of trouble exporting only Co[7]. It gave me part and wire errors. I ended up just exporting all Co[0:7] ports in the Full Adder. Overall this was a very enjoyable lab and I feel much cooler now that I have designed my own ALU.