Implement function with 4:1 & 2:1 Multiplexers

Discussion in 'Homework Help' started by tquiva, Nov 13, 2010.

  1. tquiva

    Thread Starter Member

    Oct 19, 2010
    I'm trying to implement four functions using a minimum number of 2:1 and 4:1 muxes with NO additional gates.

    This is my truth table:

    Right now, I'm currently working on function Z.
    I grouped the rows into pairs accordingly:

    When ABC=000, Z = D
    When ABC=001, Z = D
    When ABC=010, Z = D
    When ABC=011, Z = D

    When ABC=100, Z = D'
    When ABC=101, Z = D'
    When ABC=110, Z = D'
    When ABC=111, Z = D'

    So therefore I would need a mux with 8 data inputs?
    I put two 4:1 muxes together, with the select inputs labeled with A, B, C
    And I just labeled the data inputs by D.H (high), or D.L (low) according to the pairs above


    This is what I have so far for function Z.
    I really don't know how to label the pins or make the connections to connect both muxes together. Could someone please help me on this?

    I edited the above circuit to this one. But I still don't know how to cascade several muxes. I don't know where to connect the select inputs and other connections. Could someone please help me asap?
    Last edited: Nov 13, 2010
  2. mik3

    Senior Member

    Feb 4, 2008
    Connect B and C inputs to S1 and S0 of both multiplexers respectively. Use A input to select which multiplexer is active. When A=0, the top multiplexer shall be active (connect to A via NOT gate) and when A=1 the bottom multiplexer shall be active (connect directly to A). However, you don't need these multiplexers to achieve that. Z=D when A=0 and Z=D' when A=1, thus a simple logic circuit can achieve this.
    tquiva likes this.
  3. tquiva

    Thread Starter Member

    Oct 19, 2010
    thank you!