EKT 124 MUX AND DEMUX 1 Multiplexing and

EKT 124 MUX AND DEMUX 1

Multiplexing and demultiplexing are used when data from several sources are to be transmitted over one line to a distant location and redistributed to several destinations. The data selection function (Taken from Floyd 11 th ed pg. 30 Figure 1 -24) Floyd, Digital © 2009 Pearson Education, Upper Saddle River, NJ

Multiplexer (MUX) – Data Selector v A multiplexers (MUX) is a device that allows digital information from several sources to be routed onto a single line for transmission over that line to a common destination. v The basic multiplexers has several data input lines and a single output line. It also has data- select inputs, which permit digital data on any one of the inputs to be switched to the output line 3

Functional Diagram of a MUX 4

Functional Diagram of a MUX A multiplexer has N control inputs 2 N data inputs 1 output (Z) 2 N N A multiplexer routes (or connects) the selected data input to the output. The value of the control inputs determines the data input that is selected. 5

MUX – Function Table and Boolean Expression MSB A B Z 0 0 I 0 0 1 I 1 1 0 I 2 1 1 I 3 LSB Z = A′. B'. I 0 + A'. B. I 1 + A. B'. I 2 + A. B. I 3 6

MUX – Function Table and Boolean Expression MSB A B C Z 0 0 0 I 0 0 0 1 I 1 0 I 2 0 1 1 I 3 1 0 0 I 4 1 0 1 I 5 1 1 0 I 6 1 1 1 I 7 LSB Z = A′. B'. C'. I 0 + A'. B'. C. I 1 + A'. B. C'. I 2 + A'. B. C. I 3 + A. B'. C'. I 4 + A. B'. C. I 5 + A'. B. C'. I 6 + A. B. C. I 7 7

MUX – Output Waveforms in relation with the Data-Input and Data-Select waveforms q. The binary state of the data-select inputs during each interval determines which data input is selected. q. Here the data-select inputs go through a repetitive binary sequence 00, 01, 10, 11, 00 and so on. 8

Designing logic circuit using MUX 9

Designing logic circuit using MUX 10

Cascading MUX Using three 2 -1 MUX to make one 4 -1 MUX S 1 S 0 F 0 0 I 0 0 1 I 1 1 0 I 2 1 1 I 3 11

Cascading MUX Example: Construct an 8 -to-1 multiplexer using 2 -to-1 multiplexers. S 2 S 1 S 0 F 0 0 0 I 0 0 0 1 I 1 0 I 2 0 1 1 I 3 1 0 0 I 4 1 0 1 I 5 1 1 0 I 6 1 1 1 I 7 I 0 I 1 I 2 I 3 F 2 -1 MUX S I 4 S 2 E E I 5 I 6 I 7 12

Demultiplexer : DEMUX It reverses the multiplexing function. It takes data from one line and distributes them to a given number of output lines. It is also known as a data distributor. A demultiplexer takes a single input and distributes it over several outputs. Compares to MUX : A multiplexer takes several inputs and transmits one of them to the output. 13

DEMUX : Functional Diagram A demultiplexer switches (or routes) data from one input to 2 N outputs, where N is the number of select inputs. 14

DEMUX : Output Waveforms 15

DEMUX Out 0 I Out 1 In Out 2 Out 3 S 1 S 0 W X Y Z W = A'. B'. I X = A’. B. I Y = A. B’. I Z = A. B. I A B W X Y Z 0 0 I 0 0 1 0 0 0 I 0 1 1 0 0 0 I 16

Examples �Design a circuit, using 8 -to-1 Mux to realize the boolean expression given below: FA, B, C, D = Ʃ(1, 3, 4, 11, 12, 13, 14, 15) �Construct an 8 -to-1 multiplexer using 2 -to-1 multiplexers. Label the input, output and selector clearly in your design. 17

Thank You 18