ELEC1303 - Lecture 9

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ELEC1303 - Lecture 8
Multiplexers - Slides

Multiplexers

• Multiplexing and demultiplexing are used when data from several sources are to be transmitted over a single communication channel or medium and redistributed to several destinations

• A multiplexer is a digital circuit that selects and combines multiple input signals into a single output signal
  • Also known as a data selector

• 4-to-1 Multiplexer:

  
  Note: there is an additional input/s $S$ that control which of the other inputs is connected to the output

• Truth Table:

  

Implementing Boolean Function using Mux

• Any Boolean function can be implemented using a multiplexer
• If a Boolean function has $N$ inputs:
  • A single 2${}^N$-to-1 multiplexer is sufficient
  • Or a smaller multiplexer with logic gates in front of the input data lines

• Essentially, $a,b,c$ will choose which input is chosen

Example using a smaller Mux: slides

• Multiplexers can be cascaded to build larger multiplexers

Demultiplexers

• A demultiplexer is a digital circuit that performs the opposite function of a multiplexer
  • Takes single input, routes to one of several output lines
  • Enable distribution of a single input to multiple destinations

Applications of Multiplexers

• Can be used to implement unsimplified Boolean functions
• Programmable logic devices
• Data routing
• Parallel-to-serial and serial-to-parallel conversion

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ELEC1303 - Lecture 10