How to use a 8-bit multiplexer

Discussion in 'Homework Help' started by yjpang84, Sep 10, 2006.

  1. yjpang84

    Thread Starter New Member

    Sep 10, 2006
    1
    0
    Guys im desperate..

    this is the qn: Z is a boolean function of 3 input variables A,B and C. If A=C; else Z=0.

    Design and draw a clearly labelled diagram to implement Z using only one 8-bit multiplexer.

    i don't even understand the question. please enlighten. :confused:
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    What happened to "then?" Is the "then" supposed to be "Z=1?" Is B a "red herring" variable?

    I would contact the instructor to see if there is a typo.
     
  3. rishid

    New Member

    Oct 24, 2005
    8
    0
    Truth table for this is:
    A B C | Z
    0 0 0 | 1
    0 0 1 | 0
    0 1 0 | 1
    0 1 1 | 0
    1 0 0 | 0
    1 0 1 | 1
    1 1 0 | 0
    1 1 1 | 1

    Then I think you just use A,B,C as the select bits in the 8bit mux and draw either 1 or 0's as in puts depedning on the value of Z for the specific mux input
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    I think you are going to need to incorporate a 4-input "OR" gate into which you will need to feed the appropriate outputs of the mux to complete the implementation.

    hgmjr
     
  5. Papabravo

    Expert

    Feb 24, 2006
    9,898
    1,722
    No need for the 4-input gate. The single output of the mux is all you need. The select inputs A, B, and C "select" one of the constant inputs to route to the output. It could hardly be simpler.
     
  6. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    My bad. Papabravo is correct. I was thinking of 3-in / 1-of-8 out decoder when I recommended an OR gate.

    hgmjr
     
  7. Papabravo

    Expert

    Feb 24, 2006
    9,898
    1,722
    It's an easy mistake to make without a diagram. Although I have known about this technique since I was an undergraduate, I have never had occasion to use it in a career that has spanned nearly four decades.
     
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