Log in and create a cs31/weeklylab/week03 subdirectory and copy over
some files from my public/cs31/week03/ directory into your subdirectory:
cd
cd cs31
cd weeklylab
mkdir week03
cd week03
pwd
cp ~newhall/public/cs31/week03/* .
ls
decoder.circ firstcircuit.circ
Goals for this week:
- Learn how to use logisim, and start the tutorial
- Introduction to lab 3
Logisim
I suggest working in the CS labs on logisim rather than logging in
remotely. Logisim will run very slowly if you are remotely logged in
due to X forwarding events (use ssh -Y on Mac or Linux to enable
X-forwarding, on Windows you need to install an X server to run
logisim remotely). Alternatively, you can install
logisim on your own computer, and scp your .circ file to/from your computer
to your CS account. We are using version 2.7. Make sure to install
the same version. Also, if you do this, you need to ensure that your
circuit file works on logisim running on our system.
The Logisim simulator
This week we will start using the Logisim simulator to create circuits
and to see what the does given different input. We will learn more
Logisim in class, but today I want to step through a few examples using it.
The Logisim web page has user documentation that will be very helpful for the next lab
assignment. We are using version 2.7.
$ logisim # start new project
$ logisim proj_file.circ # edit an existing project
We will start with firstcircuit.circ, and try builiding a simple AND
circuit and some tester circuitry around it:
$ logisim firstcircuit.circ
Next, we are going to build a 2-to-4 1 bit decoder (2 1 bit inputs,
4 1 bit outputs).
A --------o
| AND --------- 1 if both A and B are 0
B --------o
| |
*--|--o
| | AND --------- 1 if A is 0 and B is 1
---*---
| |
*--|--
| | AND --------- 1 if A is 1 and B is 0
---*--o
| |
*--|--
| | AND --------- 1 if A is 1 and B is 1
---*--
This we will build as a circuit in logisim
(Project:Add Circuit). Then we will incorporate this into some tester
circuitry in the main circuit:
$ logisim decoder.circ
Next, step through the Beginner's tutorial and try building the XOR circuit.
Lab 3 Intro
Click on the lab 3 link off the class schedule for week 3.
We will go over the lab 3 assignment and requirements.