o/p 4-bit comparator

Discussion in 'Homework Help' started by zulfi100, Mar 24, 2013.

  1. zulfi100

    Thread Starter Member

    Jun 7, 2012
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    Hi,
    Kindly guide me with the output of 2 2-bit comparators (i think its a 4-bit magnitude comparator) constructed by combing 2 xnor gates whose o/p is connected to a AND gate. When input 11 and 00 is supplied, i am getting 1 output though 11 and 00 are not same. Kindly guide me.

    Zulfi.
     
  2. WBahn

    Moderator

    Mar 31, 2012
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    Start with the boolean expression for your circuit. What is it?
     
  3. zulfi100

    Thread Starter Member

    Jun 7, 2012
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  4. WBahn

    Moderator

    Mar 31, 2012
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    Now, what is another name for the XNOR gate? Specifically, it is HI when both inputs are ...?

    In the example you started with, the four bits that were applied, 11 and 00, how did those four bits map to the two 2-bit numbers being compared?
     
  5. zulfi100

    Thread Starter Member

    Jun 7, 2012
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    Ans. When inputs are same. Sorry I dont know the other name (wiki says enor or exnor).
    Sorry. I dont understand this mapping term. 1100 is mapped to 11 xnor 00.

    Kindly guide me.

    Zulfi.
     
  6. WBahn

    Moderator

    Mar 31, 2012
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    It is also known as the EQ, or EQUALITY, gate.

    Well, look at the slides that you linked. In particular, slide #6.
     
  7. zulfi100

    Thread Starter Member

    Jun 7, 2012
    320
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    Okay. Thanks. I got it now. I should be:
    comparing 00 & 11
    so (0 xnor 1) and (0 xnor 1)= 0 (not same).

    Thanks for your time.

    Zulfi.
     
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