1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Demultiplexer 8 to 1

  1. Oct 21, 2009 #1
    I understand a demultiplexer has only one input and many outputs and a multiplexer only has one output and many outputs, I figured out my truth table for a 8 to 1 multiplexer which is

    S2 S1 S0 OUT
    0 0 0 D0
    0 0 1 D1
    0 1 0 D2
    0 1 1 D3
    1 0 0 D4
    1 0 1 D5
    1 1 0 D6
    1 1 1 D7

    to figure out my truth table for my demultiplexer i get quite confused on the proper way to go about it
  2. jcsd
  3. Oct 21, 2009 #2


    User Avatar

    Staff: Mentor

    Seems like you are missing something in your truth table above, and that is part of what is confusing you about the demux circuit.

    You show the 3 control inputs, but you should also show the 8 inputs and one output. When an input is selected byt the 3 control inputs, the other inputs are don' cares (X). The output value is the value of the selected input, i.e., 0-->0 and 1-->1.

    So for your demux table, you show the 3 control inputs, and one input, then show the values of the 8 outputs. It's a 16 row table, I believe. You will also need to define whether the non-selected outputs are 0 or 1 by default.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Demultiplexer 8 to 1
  1. 8:1 mux simulation (Replies: 1)