A multiplexor is a combinational circuit having many inputs which allows for the outputting a single data input at a time by using selection input lines. A multiplexor has

2^{n}data input lines,nselect input linesand asingle output.

### Discussion by analogy : A Television remote control used to access 4 channels

*Teacher describes a remote control with 2 buttons that can be toggled on and off to switch between 4 channels*

## A 4 to 1 multiplexor

The truth table is shown below:

s_{1} | s_{2} | Output at F |
---|---|---|

0 | 0 | x_{1} |

0 | 1 | x_{2} |

1 | 0 | x_{3} |

1 | 1 | x_{4} |

Note that the data from any input line can be either a 0 or 1 instantaneously depending what the input at a the time. For example, let us consider the situation where over the next 4 cycles of execution on a cpu that

- dataline
produces 0011 on each cycle respectively,*x*_{1} - dataline
produces 1100 on each cycle respectively; and*x*_{2} - during cycles 1 and 2,
**s**and_{1}**s**are 0 and 0 respectively_{2} - during cycles 3 and 4,
**s**and_{1}**s**are 0 and 1 respectively_{2}

The resulting output at *f* over the four cycles are 0000.

That is, two bits of data from ** x_{1}**, then two bits of data from

*x*_{2}.In sequence , we selected

**x**for 2 consecutive cycles, then

_{1}**x**for another 2 consecutive cycles.

_{2}### Attribution to media used in this post

User:Mdd4696, Public domain, via Wikimedia Commons© 2021 Vedesh Kungebeharry. All rights reserved.