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Build a XOR with a MUX and a Invertor?

Discussion in 'Electronic Basics' started by Al Borowski, Oct 16, 2005.

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  1. Al Borowski

    Al Borowski Guest


    Input A of MUX = S1
    Input B of MUX = NOT S1
    Input S of MUX = S2


    Working out the Truth Table....

    If S1 and S2 are 0, the MUX output is S1, which is 0

    If S1 and S2 are 1, the MUX output is NOT S1, which is 0

    If S1 is 1 and S2 is 0, the MUX output is S1, which is 1

    If S1 is 0 and S2 is 1, the MUX output is NOT S1, which is 1

    Do I get the job? :)

    Al
     
  2. Davy

    Davy Guest

    Hi all,

    How to Build a XOR with a MUX(2 to 1) and a invertor?

    Any suggestions will be appreciated!
    Best regards,
    Davy
     
  3. There aren't that many ways how you can wire them together.

    Try each possible way, and figure out the truth table, and
    compare that with an XOR truth table.

    Good luck with your home work ;)
     
  4. Davy

    Davy Guest

    Hi Frank,

    It's a interview problem and I just cannot answer it.
    Anyone give an answer will be appreciated!

    Best regards,
    Davy
     
  5. Well, there's your answer then -> "I cannot answer it".
     
  6. Fred Bloggs

    Fred Bloggs Guest

    An XOR on A and B is /A*B + A*/B using obvious notation. So you would
    for example use A to drive the MUX bit select , then route B to the MUX
    0 input and /B to the MUX 1 input:
    View in a fixed-width font such as Courier.
     
  7. Fred Bloggs

    Fred Bloggs Guest

    Not with that reasoning- better luck next time....
     
  8. Fred Bloggs

    Fred Bloggs Guest

  9. I guess I'm just dense, but how is this different from Al's solution?
    Granted that you hooked it up a bit different than Al, but the outcome
    is the same AFAICT.
     
  10. Jim Thompson

    Jim Thompson Guest

    Yep. An XOR is just a 4-quadrant multiplier. And that architecture,
    in high speed circuits, has less glitch issues (if implemented with
    all inputs differential, as in ECL/PECL).

    ...Jim Thompson
     
  11. Fred Bloggs

    Fred Bloggs Guest

    Fastest possible binary multiplier known:)
    View in a fixed-width font such as Courier.
     
  12. John Fields

    John Fields Guest

     
  13. Fred Bloggs

    Fred Bloggs Guest

    The MUX transfer function is OUT= SEL*IN1+/SEL*IN0, the XOR is
    OUT=A*/B+/A*B, the substitution is clear, in contrast to this gibberish:
    Input A of MUX = S1
    Input B of MUX = NOT S1
    Input S of MUX = S2
    with which only the perpetually confused could not be aggravated.
     
  14. John Larkin

    John Larkin Guest

    Which is just a balanced modulator.

    John
     
  15. John Larkin

    John Larkin Guest

    Or is it that the perpetually aggravated are confused?

    John
     
  16. Fred Bloggs

    Fred Bloggs Guest

    The perpetually confused have no sense of comprehension and are
    therefore never aggravated.
     
  17. Rich Grise

    Rich Grise Guest

    What percentage of your pay do we get for getting you this
    job?

    Thanks,
    Rich
     
  18. Rich Grise

    Rich Grise Guest

    Well, I must be one of those "perpetually confused" then, because it
    was perfectly clear to me. ;-)

    Thanks,
    Rich
     
  19. Jim Thompson

    Jim Thompson Guest

    Yep.

    ...Jim Thompson
     
  20. Al Borowski

    Al Borowski Guest


    What's so confusing about that?

    Even if you didn't know what nomenclature I used, I don't think it's
    terribly hard to work out.

    "Input A of MUX...Input B of MUX" implies I am calling the 2 inputs of
    the MUX A & B.

    "If S1 is 1 and S2 is 0" implies that S1 and S2 are the inputs to the
    system.

    "Input B of MUX = NOT S1 " implies that I am using the NOT gate to
    invert an input, and attach it to a MUX input.

    Admittedly a picture would have been clearer, but it would have taken me
    longer to draw then it took me to solve the problem :)

    I didn't bother consciously making the substitution. I just mentally
    combined the parts in my head for twenty seconds until I found something
    that worked.

    cheers,

    Al
     
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