trabalho Counter to 7 Segment Display with JK Flip-flops and Logic Gates (1) (1) - Multisim Live
How to design a synchronous counter 4 bit using JK flip flop that can count up even numbers from 0 to 14, and count down odd numbers from 15 to 0 in 1 system - Quora
What is the circuit diagram of a Mod-15 asynchronous down counter? - Quora