# Spring 2002 CSCI 255 Lab 2

This lab is scheduled for 6 & 7, February.

## First things first

If you didn't finish Lab 1 on account of Linux account problems, do so now.

## Goals and Methods

This week we'll use an extremely simple digital logic schematic design and simulation tool to build a couple of digital circuits.

We'll be using a program called MultiMedia Logic, a Freeware program that can be downloaded for any Windows system.

It's not hard to get MultiMedia Logic started from the Windows Start button. If you need help, your lab instructor will be glad to guide you.

As soon as you have MultiMedia Logic running, go to the Help pulldown menu and select Tutorial. Read at least the first four pages of the Tutorial before continuing with this lab.

Two incomplete MultiMedia design files, Lab2a.lgi and Lab2b.lgi, are needed for this lab. You can download these as either a Windows self-extracting exe file or a Zip file.

## Part A

Using MultiMedia Logic, open Lab2a.lgi.

Go to the Simulate pulldown menu and select Run to start an interactive simulation. Now press the input switches to toggle the three inputs between 0 and 1. When you have determined which half of the full adder you have, stop the simulation.

Now construct the other half of the full adder. This isn't hard. You'll have to drag the appropriate gates from the tools pallete

and place them into your circuit. You also need to add a new LED and do some wiring. You'll probably want to select at least one gate and set its properties. This is now you change an AND to a NAND and set the number of gate inputs.

When you've completed the full adder, save it back as Lab2a.lgi and show your work to the lab instructor.

## Part B

Now open Lab2b.lgi.

Run the circuit and convince yourself that it really does compute the expressions NOT X AND Y and NOT X OR Y.

Your job is to modify the implementation of this circuit so that is uses only inverters and NAND gates. Do this using the following two facts:

• NAND(A, B) = NOT(AND(A, B))
• OR(A, B) =NAND(NOT(A), NOT(B))

The second equality is called de Morgan's law. We'll be studying it in class next week.

Again, when you're done with Lab2b.lgi, show your work to the lab instructor.

## Going home

If you've shown the lab instructor your work, you can go home.