Multiplexers & Demultiplexer

Multiplexers & Demultiplexers Digital Electronics Lesson 2.4 – Specific Combo Circuits & Misc Topics

Multiplexer / Demultiplexer This presentation will demonstrate • The basic function of the Multiplexer (MUX). • The typical application of a MUX. • A 4-to-1 MUX designed with Small Scale Integration (SSI). • A 4-to-1, 8-to-1, & 16-to-1 Medium Scale Integration (MSI) Multiplexer / Demultiplexer MUX. • The basic function of the Demultiplexer (DEMUX). • The typical application of a DEMUX. Digital Electronics • A 1-to-4 DEMUX design with Small Scale Integration (SSI). • A 1-to-4, 1-to-8, & 1-to-16 Medium Scale Integration (MSI) DEMUX.

• A 7-segment message display using MUX/DEMUX. 2

What is a Multiplexer (MUX)? Typical Application of a MUX

Multiple Sources Selector Single Destination • A MUX is a digital switch that Multiplexer has multiple inputs (sources) Block Diagram MP3 Player and a single output Docking Station (destination).

N • The select lines determine 2 1 D0 Output Laptop Inputs D1 (sources) (destination) Sound Card Y

which input is connected to MUX D2 MUX the output. D3 Surround Sound System • MUX Types N Digital B A Selected Source  2-to-1 (1 select line) Satellite Select 0 0 MP3  4-to-1 (2 select lines) Lines 0 1 Laptop  8-to-1 (3 select lines) 1 0 Satellite Digital 1 1 Cable TV  16-to-1 (4 select lines) Cable TV 3 4

4-to-1 Multiplexer (MUX) 4-to-1 Multiplexer Waveforms

D1 Y D1

D2 Input MUX D3 Data D2

B A D3 B A Y 0 0 D0 A Select 0 1 D1 Line 1 0 D2 B

1 1 D3 Output Y Data 5 D0 D1 D2 D3 D0 D1 D2 D3 6

Medium Scale Integration MUX What is a Demultiplexer (DEMUX)?

4-to-1 MUX 8-to-1 MUX 16-to-1 MUX • A DEMUX is a digital switch Demultiplexer with a single input (source) Block Diagram Inputs Output (Y) (and inverted output) and a multiple outputs (destinations).

Select

Enable 1 2N • The select lines determine Input Outputs which output the input is (source) (destinations) connected to. DEMUX • DEMUX Types N  1-to-2 (1 select line) Select  1-to-4 (2 select lines) Lines  1-to-8 (3 select lines)  1-to-16 (4 select lines) 7 8

Typical Application of a DEMUX 1-to-4 De-Multiplexer (DEMUX)

Single Source Selector Multiple Destinations

D1 B/W Laser Y Printer D2

DEMUX D3 Fax Machine B A

X D1 D2 Color Inkjet B A D0 D1 D2 D3 Printer

DEMUX D3 0 0 Y 0 0 0

B A Selected Destination 0 1 0 Y 0 0 0 0 B/W Laser Printer Pen Plotter 1 0 0 0 Y 0 0 1 Fax Machine 1 0 Color Inkjet Printer 1 1 0 0 0 Y 1 1 Pen Plotter 9 10

1-to-4 De-Multiplexer Waveforms Medium Scale Integration DEMUX

X Input Data 1-to-4 DEMUX 1-to-8 DEMUX 16-to-1 MUX S0 Select Select Line Outputs Input (inverted) S1 (inverted)

D1 Output Data Note : Most Medium Scale Integrated (MSI) DEMUXs , like D2 the three shown, have outputs that are inverted. This is done because it requires few logic gates to implement DEMUXs D3 11 with inverted outputs rather than no-inverted outputs. 12

Seeing Is NOT Always Believing Simple Message: All Segments On • Our lives are filled with • The circuit to the right uses electronic signs that display four 7-segment displays to display the word CIAO. In the time, temperature, or ball this circuit all displays are game score. However, what continuously illuminated,

we see is not always what is brgprecision.com each displaying one letter in really happening. the word. • In fact for most displays, the electronic-scoreboard.com • Though this method works, it individual display segments is a VERY inefficient use of are cycled through so that power. To illuminate the simple message CIAO in this only one display is on at any way, 18 segments must be given time. continuously on. • The cycle speed is so fast that digicam-tech.com • Can you think of another way nu-mediadisplays.com/signs/time- the human eye perceives that displays.php to display this message that all segments are on. 13 would use less power? 14

Multiplexed Displays Segments Let’s See How It Works

Manual Selector Demultiplexer Multiplexed Displays

• In this circuit the display segments are multiplexed, meaning that only one display is on at a time. • To display the entire word, the displays must be de-multiplexed using a 1-to-4 DEMUX. • In this example the select lines that control the DEMUX are connected to two switches. You must toggle 00, Click Schematic to Play Video 01, 10, 11 to see the entire message. (Not Practical) 15 16

Complete Design

This is a ripple counter (remember the dice game). We will learn how to design a ripple counter in unit 3. 17