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Multiplexers, full adders...

Discussion in 'Electronics Homework Help' started by power13, Nov 22, 2018.

  1. power13

    power13

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    0
    Oct 26, 2018
    Hello everyone,

    I have a problem. I have an expression F(a,b,c) with 2 cases.
    if a=0,2,5,7,8.. then F= ab +c
    else F=a+c

    a,c are 4bit binary numbers, b: 2bit number

    I have to use full adders, multiplexers 2 by 1 and logic gates.

    How I will check if a is that numbers? using multiplexers? I want a direction to this check..

    (For multiplication and addition I am using full adders)

    Thank you.
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,219
    1,857
    Nov 17, 2011
    The straightforward approach is a logic function using logic gates. The function can be created by several methods, e.g. using a Karnaugh map.
     
    power13 likes this.
  3. power13

    power13

    9
    0
    Oct 26, 2018
    a: 4 bits
    b: 2 bits

    f1= ab (if a=0,2,5,7,8)
    f1= b (if a ≠0,2,5,7,8)
    So, f1: 6 bits

    Karnaugh map for 6 bits... I think maybe there is easier way.
     
  4. power13

    power13

    9
    0
    Oct 26, 2018
    After some thought, you're right. Karnaugh map for x (4 bits). 1 if condition is true (x is one of these numbers)
    But, except logic gates, I have to use multiplexers, too.
     
  5. Harald Kapp

    Harald Kapp Moderator Moderator

    9,219
    1,857
    Nov 17, 2011
    If x then y else z
    That is exactly what a multiplexer does: generate output y or z depending on control input x.
    Now apply this to your problem. That should be easy as pie.
     
    power13 likes this.
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