How to use a 8-bit multiplexer

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

  1. yjpang84

    yjpang84 Thread Starter New Member

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    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

    thingmaker3 Retired Moderator

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    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

    rishid New Member

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    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

    hgmjr Moderator Staff Member

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    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

    Papabravo AAC Fanatic!

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    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

    hgmjr Moderator Staff Member

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    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

    Papabravo AAC Fanatic!

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    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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