Digital Logic 4-bit Multiplier/Adder

  • Thread starter roinujo1
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  • #1
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Homework Statement


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

Homework Equations


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


Adder Circuit:
upload_2016-10-10_16-10-34.png

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!
 

Answers and Replies

  • #2
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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).
 
  • #3
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Can you please show how we can use the mux to let the user choose between adder or multiplayer ?
 
  • #4
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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.
 
  • #5
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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.
should we use 4:1 mux or 2:1 mux ?
 
  • #6
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Addition and multiplication are 2 operations. What else do you want to put into the MUX?
 
  • #7
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Addition and multiplication are 2 operations. What else do you want to put into the MUX?
only addition and multiplication.
 

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