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Digital Logic 4-bit Multiplier/Adder

  1. Oct 10, 2016 #1
    1. The problem statement, all variables and given/known data
    Build a circuit that either adds or multiplies two 4-bit numbers based on a control input C(C is 1 add, C is zero multiply). Numbers are positive and negative so use two's complement. You can use muxes, Full Adder Circuits, and logic gates

    2. Relevant equations
    Multiplier circuit= upload_2016-10-10_16-2-7.png

    Adder Circuit:
    upload_2016-10-10_16-10-34.png
    3. The attempt at a solution
    So, I have built both the Full Adder(for the addition part) and the multiplier. However, I dont know how to use the muxes to get the input switching if control is 0 and 1. Since the mux only has one output, I dont understand how to connect the two circuits together. Any help is much appreciated!
     
  2. jcsd
  3. Oct 10, 2016 #2

    mfb

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    Staff: Mentor

    The mux output is the final result - one bit of the addition or multiplication depending on the state of C. Where do you expect more outputs? You'll need one mux per bit (or a mux block that can handle multiple bits in parallel).
     
  4. Apr 6, 2017 #3
    Can you please show how we can use the mux to let the user choose between adder or multiplayer ?
     
  5. Apr 6, 2017 #4

    mfb

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    This thread is half a year old.
    The multiplexer looks like every other multiplexer - for each bit, choose either input A or input B as output, depending on a control bit. Do that for all 4 bits.
     
  6. Apr 6, 2017 #5
    should we use 4:1 mux or 2:1 mux ?
     
  7. Apr 6, 2017 #6

    mfb

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    2016 Award

    Staff: Mentor

    Addition and multiplication are 2 operations. What else do you want to put into the MUX?
     
  8. Apr 7, 2017 #7
    only addition and multiplication.
     
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