CS/COE 447: Spring 2010 Lab 11

YOUR NAME:                        

YOUR PARTNER'S NAME:

Introduction to Logisim

Download logisim and then launch the application.

   http://ozark.hendrix.edu/~burch/logisim/

Part 0: The Basics (Warm-Up)
We'll begin by creating a very simple circuit just to get the feel
for placing gates and wires. 
1. Start by clicking the AND gate button. 
   This will cause the shadow of an AND gate to follow your cursor
   around. Click once within the main schematic window to place an AND
   gate.

2. Click the Input Pin Now, place two input pins somewhere to the left
   of your AND gate.

3. Click the Output Pin button. Then place an output pin somewhere to
   the right of your AND gate.

4. Click the Wire tool button.  Click and drag to connect the input
   pins to the left side of the AND gate.  You can attach the wires to
   any pins on the AND gate on the left side. Repeat the same
   procedure to connect the output (right side) of the And Gate to the
   output.

5. Finally, click the Poke tool tool and try clicking on the input
   pins in your schematic. Observe what happens. Does this match with
   what you think an AND Gate should do?

****Part 1: Sub-Circuits

Just as programs can contain helper functions, a schematic can contain
subcircuits. In this part of the lab, we will create several
subcircuits to demonstrate their use.  

Create a new schematic for your work (File --> New).  

Create a new subcircuit (Project --> Add Circuit ). You will be prompted for a name for the
subcircuit; call it NAND.  

In the new schematic window that you see create a simple NAND circuit
with 2 input pins on the left side and an output pin on the right
side.

Go back to your main schematic by double-clicking main in the circuit
selector at the left of the screen.

Your original (blank) schematic will now be displayed, but your NAND circuit has been
stored.  

Now, single click the word NAND in the list. This will tell Logisim that you wish to add your
NAND circuit into your main circuit.  

Try placing your NAND circuit into the main schematic. If you did it
correctly, you should see a gate with 2 input pins on the left and one
output pin on the right. Try hooking input pins and output pins up to
these and see if it works as you expect.

Repeat these steps to create several more subcircuits: NOR, XOR, 2 to
1 MUX, and 4 to 1 MUX. Do not use any built in gates other than AND,
OR, and NOT. However, once you've built a subcircuit, you may use it
to build others.

Checkoff:
Show your circuits (NAND, XOR, 2 to 1 MUX, and 4 to 1 MUX) to
your TA.

****Part 2: From Truth Table to Schematic
Given the following truth table, complete the tasks
below.

in1 in0    out1 out0
 0   0      0    1
 0   1      1    0
 1   0      1    1
 1   1      0    0 
1. From the truth table above derive the Canonical Sum of Product boolean
equations for out1 and out0.

2. Using the rules of boolean algebra simplify your boolean equations,
if you can.

3. Implement your simplified boolean equations in your main schematic
in Logisim. Feel free to use any of the subcircuits you designed
earlier if they would help. Be sure you label your input and output
pins appropriately using the Text To use the text tool, select the
tool and click on your schematic and start typing. If you make a
mistake, you can edit the text by selecting your text object using the
selection tool, and edit the "Text" property in the property list
below the circuit browser (window where you can select your tools and
circuit)

Checkoff:
Show your canonical SOP of the truth table.
Show your boolean algebra simplifications to your TA.
Show your working schematics to your TA.