Implementing full adder Using 8-1 multiplexer??

Discussion in 'Homework Help' started by dogar sahab, Apr 25, 2008.

  1. dogar sahab

    Thread Starter Active Member

    Mar 15, 2008
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    0
    Please I need help for implementing the full adder using the following circuit in the attachment..
    I am fnding problem in finding the carry-output using this circuit...
    please help me how can i get carry output of full adder using this circuit..
    I can find sum through this...
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Is it possible they want you to program the output truth table on this? An 8 channel multiplexer has 3 select bits (3 bit word), 8 inputs, 1 output, and a select line. You can program a truth table by tieing the inputs to a 1 or a 0 depending on what you want the output to be for the select bit.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    I moved this to the Homework section. Besides Bill's advice, you will find several threads that had assignments very similar to yours.

    They all start from the truth table.
     
  4. dogar sahab

    Thread Starter Active Member

    Mar 15, 2008
    116
    0
    we are given the truth table and we are asked to implement it..the truth table is the customary truth table of FULL ADDER..The problem is that how can I interpret CARRY_INPUT??
    we are asked to simulate it on BREADBOARD!!
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Several ways actually, you can use a second multiplexer with a AND truth table, or use a gate directly, depends what the instructor has told you. To add 3 binary digits and come out with 4 bits is going to require a miniumum of 3 multiplexers, 1 per output bit, and possibly another for carry. Multiplexers are basically 1st generation programmable logic arrays, wasteful but occasionally useful for the purpose, or maybe ROMs is a better analogy.
     
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