CS31 Weekly Lab Week 3

Logisim: Logic Simulator

Goals for this week:

  1. Gain experience with the Logisim logic circuit simulator.
  2. Build an XOR component.
  3. Make progress on Lab assignment #3.

Logisim Demo

For this lab, we'll be using Logisim to create and test digital circuits using the logic gates (AND, OR, NOT, etc.) we've been talking about in class.

I suggest working in the CS lab on Logisim rather than logging in remotely. Logisim will run very slowly if you are remotely logged in due to X forwarding events (i.e., using ssh -Y on Mac or Linux to enable X-forwarding). Alternatively, you can install Logisim on your own computer, and use git to push/pull your .circ file to/from your computer and your CS account. If you do this, you still need to ensure that your circuit file works on Logisim running on our system, the lab is where we'll be doing the grading!

We'll start by demoing the basics of Logisim (adding gates, inputs, and outputs), and then Kevin will demo building a bit swapper for 4-bit values.

Your turn!

Work with your partner to build an XOR gate using only AND, OR, and NOT gates (plus inputs and outputs). Build your gate as a new component that you can then deploy in main.

Refer to the Logisim beginner's guide for the details of building an XOR gate, including a circuit diagram.

Lab 3 Assignment

Next, let's look over the Lab 3 assignment and then get started on it!