DIGITAL ELECTRONICS Multiplexer

Chapter 10Chapter 10

BINARY ARITHMETIC,

DECODING AND MUX LOGIC UNITS

Ch10L5-"Digital Principles and Design", Raj Kamal, Pearson Education, 2006 2

Lesson 5

Multiplexer


Outline

• Multiplexer • 2 of 1 and 4 of 1 line multiplexer• 8 of 1 • 4 of 16 line multiplexer• Multiplexers Arranged as tree


Multiplexer• A circuit that sends the binary information

from one of the input line to the output and that line is selected as per the address or channel select bits.

• A circuit that selects the input line among the input lines as per channel-selector logic-inputs and gives that line input at the output. A multiplexer selects a unique input line according to the address or channel selector inputs to it


Multiplexer Applications

• Sharing the Boolean function circuit outputs, ports, devices and resources

• Logic Design of circuits


n to 1 Multiplexer

• A circuit, which takes the 2n -input line but presumes with only one = active and gives that at output

• Selection is using n-address (channel) select bits


Outline

• Multiplexer • 2 of 1 and 4 of 1 line multiplexers• 8 of 1 line multiplexer• 4 of 16 line multiplexer• Multiplexers Arranged as tree


2-channel input-selector (2 to 1 multiplexer)

• One channel selector pin A (= 0 for channel or Boolean function F0 and = 1 for channel F1)


Multiplexer as Line Selector • Assume that we have two logic circuits

that provide the outputs. One is for a logic function F0 and other is for F1. We have to select only one by giving appropriate instruction at the pins called address pin or channel select pin A. A multiplexer will select for the output only one of F0 or F1


2 of 1 Multiplexer

F0 F1 0 F0

Inputs Select Input Output I0 I1 A Y

F0 F1 1 F 1

F0 or F1I1I0

A

F0F1


4 of 1 Multiplexer

F0 F1 F2 F3 0 0 F0

Inputs Select Input Output I0 I1 I2 I3 A1 A0 Y

F0 F1 F2 F3 0 1 F1F0 F1 F2 F3 1 0 F2F0 F1 F2 F3 1 1 F3


4 of 1 Multiplexer

YF0 or F1 orF2 or F3I1

I0

A0

F0F1

I3I2F2

F3

A1


Outline



8 of 1 Multiplexer

I7 ..... I0 001 I1

Inputs OutputI7 ..... I0 I0

Y0

Select Inputs 000

I7 ..... I0 ... .I7 ..... I0 111 I7


8 of 1 Multiplexer

YF0 or F1 orF2 or F3I1

I0

A0

F0F1

I3I2F2

F3

A1

I5I4F4

F5

I7I6F6

F7

A2


Outline

• Multiplexer • 2 of 1 and 4 of 1 line multiplexers• 8 of 1 line multiplexer• 4 line of 16 line multiplexer • Multiplexers Arranged as tree


16 of 1 (16 line to 4line) Multiplexer with one input and one output control

(enabling/disabling) pin

A1A0

G

A15 ...

G = 0enables the output

Y


16 of 1 (8 line to 3 line) Multiplexer with one output control (enabling/disabling) pin

A2A0

Y

OE

A1A0

A15 ...

OE = 0meansenable the input


Outline



Tree

• We get the (m of 1) multiplexing from i numbers of the (m’ of 1) multiplexers when the multiplexers arranged as a tree

• Here m = i.m’ where i is an integer and m’ = 2n where n is the number of channel selector lines at each of the i multiplexers


Multiplexer Tree

YF0 or .. or F15

I0.I3

A3A2A1A0

I4..I7

I8..I11

I12..I15


Summary


Multiplexer• A multiplexer provides output path

(channel) for the one channel data from the number of channels at a given instant.

• Its important application is in sharing the circuits, ports, devices and resources.

• A number of multiplexers can be arranged in tree topology to obtain a bigger numbers of channel-multiplexer

• A multiplexer has control gate pin(s) for output enable


End of Lesson 5 on

Multiplexer


THANK YOU

DIGITAL ELECTRONICS Multiplexer

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