I have been learning counters and am able to design an asynchronous UP counter with JK flip flops in Multisim, however I am unable to convert it to an asynchronous DOWN counter.

My UP counter counts properly 0-1-2-3-0-1-2-3, however my DOWN counter counts 0-2-1-3-0-2-1-3. I want it to count 3-2-1-0-3-2-1-0. How should I fix my DOWN counter?

My UP counter enter image description here

My DOWN counter enter image description here


2 Answers 2


I think I've got it, it counts 0-3-2-1-0-3-2-1-0

enter image description here

  • 2 10 to 11
  • 1 01 to 10
  • 3 11 to 01
  • 0 00 to 00

  • What is the difference ? swapped clock input position caused a problem.

    • swap out bits and invert LSB
  • note you can XOR output to count down


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