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
Synchronous Counter and the 4-bit Synchronous Counter
4-Bit Synchronous Up Counter
Synchronous Counter and the 4-bit Synchronous Counter
DeldSim - 4-Bit Up Counter
74LS191 Synchronous 4-Bit Up/Down Counter IC With Mode Control