Question about multiplexers

Discussion in 'Homework Help' started by dre, Dec 17, 2009.

  1. dre

    Thread Starter New Member

    Dec 17, 2009
    I'm trying to understand a slide from my notes. I do understand what we're trying to do but not why we are doing it. Basically why are we expanding F so that each term has a B? After the "now compare with:" line where did we get that equation from? Also why are we setting the I0 to 1, the I1 to 0 and the I2 and I3 to C?

    Could someone please explain this, the slide is from my notes which I have uploaded to tinypic for viewing.

    Thanks for any help.
  2. zgozvrm

    Active Member

    Oct 24, 2009
    A & B are the control lines to the MUX so every possibility of A, B, C (all 8 of them) should contain A & B terms so that they can control the MUX.

    Recall how the select lines (A & B) choose an input line to pass to the output. There are 2 select lines, therefore 2^2 = 4 input lines.

    For each possible input for A, B, & C, what should the output be? (Draw a truth table).

    The inputs to a n-input MUX are typically labeled I_0, \: I_1, \: I_2, \: ... , \: I_{n-1} where input I_0 is selected by setting the select lines to 0, 0. Input I_1 is selected by setting the select lines to 0, 1, etc.