Circuit Implementation Using Multiplexers


Theory Theory

Algebraic Manipulation Algebraic Manipulation

Karnaugh Maps Karnaugh Map Method

Numerical Method Numerical Method

Simulation Simulation

Exercises Exercises


Theory Theory: What is a multiplexer?

It quite often happens, in the design of large-scale digital systems, that a single line is required to carry two or more different digital signals. Of course, only one signal at a time can be placed on the one line. What is required is a device that will allow us to select, at different instants, the signal we wish to place on this common line. Such a circuit is referred to as a Multiplexer.

A multiplexer performs the function of selecting the input on any one of 'n' input lines and feeding this input to one output line.

Multiplexers are used as one method of reducing the number of integrated circuit packages required by a particular circuit design. This in turn reduces the cost of the system.

Assume that we have four lines, C0, C1, C2 and C3, which are to be multiplexed on a single line, Output (f). The four input lines are also known as the Data Inputs. Since there are four inputs, we will need two additional inputs to the multiplexer, known as the Select Inputs, to select which of the C inputs is to appear at the output. Call these select lines A and B.
The gate implementation of a 4-line to 1-line multiplexer is shown below:

Implementation of a multiplexer

The circuit symbol for the above multiplexer is:

Multiplexer circuit symbol

Before continuing with this section, you should make sure you are familiar with all the topics covered so far:


There are three methods for implementing a circuit using multiplexers. These are:

Algebraic Manipulation Algebraic Manipulation

Karnaugh Maps Karnaugh Map Method

Numerical Method Numerical Method


Simulation Labview Simulation

Here are some new simulations of multiplexers. There is a static multiplexer where you have to operate all the switches and there is one with a clock input where the output can be seen graphically.

Instructions for using LabVIEW on the University of Surrey network

Instructions for using LabVIEW elsewhere

Static Multiplexer exe (For Windows. LabVIEW runtime engine for Windows required)

Static Multiplexer (For UNIX. LabVIEW runtime engine for UNIX required)

vi Static Multiplexer vi (LabVIEW development environment required)

Clock Input Multiplexer exe (For Windows. LabVIEW runtime engine for Windows required)

vi Clock Input Multiplexer vi (LabVIEW development environment required)

 


Exercises Exercises

Design multiplexer implementations for the following functions using the numerical method.
The simulation should be used to check the workings.

Problem 1

Problem 2

Problem 3

Problem 4

Problem 5


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Composed by David Belton - April 98

Updated by Richard Bigwood 2005