Multiplexers/ Demultiplexers

Multiplexer

Combinational circuit that selects binary information from one of many input lines and directs information to a single output line.

Multiplexer ctd …

Selection inputs.2n input lines.n selection inputs. Data selector

Selects one of many inputs and steers binary information to output line.

Function table

A B f

0 0 C0

0 1 C1

1 0 C2

1 1 C3

Decoders in Multiplexers

AND gates and inverters in multiplexer resemble a decoder circuit.

2n - to – 1 line MUX is constructed from n-to- 2n decoder by adding 2n input lines.

MUX blocks can be combined in parallel with common selection & enable lines.

Quadruple 2-to-1 Line Multiplexer

4 multiplexers Each capable of selecting one of two

input lines. 1A 1Y 1B Input selection line S selects one of

lines in each of four MUXs. Enable input E must be active for

normal operations.

Demultiplexer

Inverse of MUX

Demultiplexer receives information from a single line and transmits it to one of 2n possible output lines.

Selection of specific output is controlled by bit combination of n selection lines.

Demultiplexer

Demultiplexer / Decoder

Identical to 2-to 4 line decoder with enable output.

Inputs EnableDecoder S1 & S0 E

Demultiplexer

E S1 & S0