ECE 2372 Modern Digital System Design Section 4.4 Mutiplexers - Demultiplexers 1

Multiplexers/Demultiplexers Basic Structure: Multiplexing describes any system that uses a single channel to carry more than one stream of information. Digital systems use time-division multiplexing. 2

Multiplexers/Demultiplexers A basic structure for time-division multiplexing is: The switches are synchronized so that input A is connected to output A, etc. A multiplexer is an n- to-1 encoder. 3

Multiplexers/Demultiplexers A 4-to-1 multiplexer takes the form: 4

Multiplexers/Demultiplexers With logic diagram : 5

Multiplexers/Demultiplexers A demultiplexer is a 1-to-n decoder of the form : 6

Multiplexers/Demultiplexers A multiplexer – demultiplexer pair may be used as follows : 7

Multiplexers/Demultiplexers Quad Two Line – to – One Line Multiplexer. Used to select one of two 4 – bit words. 8

Quad Two Line – to – One Line Multiplexer 9

to-1 Multiplexer 10

to-1 Multiplexer 11

to-1 Multiplexer 12

to-1 Multiplexer 13

to-1 Multiplexer 14

74157 Quad 2-to-1 Multiplexer 15

74157 Quad 2-to-1 Multiplexer 16

74157 Quad 2-to-1 Multiplexer 17

74157 Quad 2-to-1 Multiplexer 18

74157 Quad 2-to-1 Multiplexer 19

74157 Quad 2-to-1 Multiplexer 20

Applications of Multiplexers Data-selection: A multiplexer may be used when one of two data sources will be selected for a digital process. This is in effect a digitally controlled selector switch. 21

Applications of Multiplexers Switching Functions: A multiplexer may be used to generate minterms. 22

Applications of Multiplexers 23

Multiplexer/demultiplexer 24