logic implementation with muxes

Discussion in 'Homework Help' started by shoot2thrill, Apr 15, 2008.

  1. shoot2thrill

    Thread Starter New Member

    Apr 15, 2008
    2
    0
    Hi, I have a question on how to implement a certain logic schematic.

    I have to use 4 to 1 muxes to implement a full adder.

    For the assignment I need to use 8 full adders to convert an 8 bit binary number to its 2s complement

    I am mostly confused on how to implement the adder, can anyone help? I can probably get the rest once the adder is implemented.
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,145
    1,791
    A single 4:1 Mux can implement any function of two boolean variables. You tie the 4 inputs to zero or one according to the function you are going to implement. The two boolean variables go to the select lines. Then what ever value the select lines take the correct value is routed to the output.

    An adder is a combinatorial circuit. You start with a truth table
    0 + 0 = 0
    0 + 1 = 1
    1 + 0 = 1
    1 + 1 = 0 plus a carry

    So the boolean function for the sum is AB' + A'B which can also be written as A .xor. B

    Clearly the boolean equation for the carry is A .and. B

    Get the idea?
     
  3. shoot2thrill

    Thread Starter New Member

    Apr 15, 2008
    2
    0
    i asked a TA about it and got it, thanks
     
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