dolby.yang is right. If 50 % duty is required
- extract pos and neg edge from input signal,
- OR them,
- give ORed output to counter with parallel loading diving by 3
- and then get the 50 percent duty by normal D trigger dividing by 2 .
You Can achieve the frequency divider by any odd number, but u have a no 50% duty cycle, but still u can achieve a 50 % duty cycle but it is complex in hardware wise u have to concentrate on both positve as well as negative edge of the clock, so need positive and negative edge triggered flip flops.
Regards
Raghu