Multiplexer

Discussion in 'Homework Help' started by hoomun, Oct 8, 2004.

  1. hoomun

    Thread Starter New Member

    Oct 8, 2004
    5
    0
    hi, im supose to complete the design of " A'B'CD'+A'B'CD+A'BC'D'+A'BC'D+AB'C'D+AB'CD'+AB'CD+ABCD " or simplifed ver of it " A'BC'+AB'D+B'C+ACD " with a multiplexer and then build the circut at uni any idea on how to do this? ( i have multisim software aswell )

    cheers
     
  2. hoomun

    Thread Starter New Member

    Oct 8, 2004
    5
    0

    any 1?
     
  3. Battousai

    Senior Member

    Nov 14, 2003
    141
    44
    Ok well begin by simplifying the expression with boolean algebra:

    A'B'CD'+A'B'CD+A'BC'D'+A'BC'D+AB'C'D+AB'CD'+AB'CD+ABCD
    ------------------ =========== ------------------ ==========

    The underlined can be grouped together:

    A'B'C(D'+D)+A'BC'(D'+D)+AB'C'(D+D')+ACD(B'+B)

    Since X+X' = 1 because when X=0, X'=1 and vice versa, this results in:

    A'B'C+A'BC'+AB'C'+ACD
    -------------- ========

    Now factor the underlined and you get:

    A'(B'C+BC')+A(B'C'+CD)

    Now what is a mux?

    A mux is just a selector. It selects between two inputs, X and Y based on the value of a select variable S.

    Let's take the B'C+BC' statement.

    Let's arbitrarily pick B as the select variable. If B=0, then BC'=0 and B'C=C. Likewise if B=1, then B'C=0, and BC'=C'.

    I think you should be able to take it from there. I believe the entire solution will require three muxes.
     
  4. hoomun

    Thread Starter New Member

    Oct 8, 2004
    5
    0

    hi thanks for the reply but i got a diff simplified ans from urs. as i staed in above it was

    A'BC'+AB'D+B'C+ACD (i used multisim!)

    now if i put that in the truth table and not worry about the equation ill get this
    from troth table:

    0
    0
    1
    1
    1
    1
    0
    0
    0
    1
    1
    1
    0
    0
    0
    1

    E0= 0
    E1=1
    E2=0
    E4=D
    E5=1
    E6=0
    E7=D

    now i used 74151N

    actually heres what i got in attachment, but it dosent work?! where did i go wrong?! (is the way i did the mux right?)

    sorry about the balck and green line i forgot to put them in.
    now the truth table i get from this mux is:

    0
    0
    0
    1
    1
    1
    0
    0
    1
    1
    1
    1
    0
    0
    0
    1

    what did i do wrong can u guys see what went wrong my head dosent work any more!!!
     
    • mux.jpg
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  5. sayan_nit

    New Member

    Sep 18, 2004
    2
    0

    u first make the truth table from the given function,then draw the implementation table.encircle the min terms.take any one of(A,B,C,D)as data i/p line & the other 3 as select i/p's.then, it's easy na? ;) ;)
     
  6. arvind

    Member

    Nov 4, 2004
    18
    0
    hi,
    u can use a 16 to 1 mux, give the four conrol inputs as
    s0 A
    s1 B
    s2 C
    s3 D

    and keep the other inputs at following logic values,

    e0 0
    e1 0
    e2 1
    e3 0
    e4 1
    e5 1
    e6 0
    e7 0
    e8 0
    e9 1
    e10 1
    e11 0
    e12 1
    e13 1
    e14 0
    e15 1
    ur purpose will be solved
    ps: keep the mux in enable mode :rolleyes: :rolleyes: :rolleyes: :) :) :) :D :D :D
     
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