Hi,
Do you use CTimer module or SCTimer/PWM module to generate the PWM signal? If you use CTimer to generate the PWM signal, as you know that the PWM Reset match register will be
180MHz/20KHz=9K
so it is okay to set the match register as 9000 which reset the counter.
If you use SCTimer/PWM module, you can set the limit register as 9000, which sets up the PWM frequency.
Hope it can help you
BR'
XiangJun Rong