---
description: In this lab, we are going to design some common combinational devices, we will start by designing a binary magnitude comparator.
---
<h1 style='border: none'><center>Digital Design Lab 6</center></h1>
<h2 style='border: none'><center>Combinational Designs I</center></h2>
<h5><center>The Islamic University of Gaza<br>Engineering Faculty<br>Department of Computer Engineering</center></h5>
<h6>Authors: Usama R. Al Zayan and Enaam Rajab<span style="float:right">2022/10/28</span></h6>
<h6>Parts of this Lab were adapted from work done by Mohammed Nafiz ALMadhoun and Mai Z. Alyazji.</h6>

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## Introduction

In this lab, we are going to design some common combinational devices, we will start by designing a binary magnitude comparator.

## Magnitude Comparator

We will start our magnitude comparator by comparing only two bits, our system will have two inputs (`A` and `B`), and we will have three outputs (`A=B`, `A>B` and `A<B`).

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| A | B | A = B | A > B | A < B |
|:---:|:---:|:-----:|:-----:|:-----:|
| 0 | 0 | | | |
| 0 | 1 | | | |
| 1 | 0 | | | |
| 1 | 1 | | | |

The problem with this device is that we couldn't extend it to compare multi-bits numbers, so we need to create a similar device but it should take the output of the previous bit comparator, so it can cascade the results.

<center>

One Bit Comparator with Cascading
</center>

And this is the internals of it:

<center>

One Bit Comparator
</center>

Note that this device is useless and slow, usually, you will find the same idea of cascading but with a bigger number of bits (e.g 8-bit comparator with cascading).

## KL-33002 module

* **Block c** of module **$KL-33002$**: 1-bit Comparator constructed with basic logic gates. Connect inputs A and B to data switches SW1 and SW2, connect outputs F1, F2, F5 to LEDs L1, L2, L3 respectively.
* **Block d** of module **$KL-33002$**: will be used in task 1. U6 is a `74LS85` 4-bit comparator IC, Connect inputs A>B to SWI , A=B to SW2 , A<B to SW3 . Connect inputs A1~A4 and B1~B4 of the 7485 to DIP Switches DIP1.0~DIP1.3 and DIP2.0~DIP 2.3 respectively. See the datasheet for more details.


## Lab Tasks

### Task 1: BCD Compartor

Using `74LS85` IC (4-bit comparator) or Block d of module `KL-33002`, you will need to design a circuit that detects if a number is above 9, you will need 4 bits as inputs from the switches, and the other 4 bits from the comparator should be constant (9).

## DataSheets
Please find the datasheets here:

**$74/08$** [DM74LS08 Quad 2-Input AND Gates](https://cdn.datasheetspdf.com/pdf-down/7/4/L/74LS08_FairchildSemiconductor.pdf).
**$74/85$** [DM74LS85 4-Bit Magnitude Comparator](https://cdn.datasheetspdf.com/pdf-down/7/4/L/74LS85_FairchildSemiconductor.pdf).
**$74/138$** [DM74LS138 3-to-8-line decoders](https://cdn.datasheetspdf.com/pdf-down/7/4/L/74LS138_FairchildSemiconductor.pdf).

<span style="color:#e20000" >**DON'T POWER UP THE KL-31001 WITHOUT MY PERMSIONS.**</span>

<center style="font-size: 28px">Good luck in your midterm exams ❤</center>

###### tags: `Digital Design` `Digital` `IUG` `Computer Engineering`
<center>End Of Lab 5</center>