how to set pic18f452 to its max pwm frequency

[lgeorge123]

using pic18f452 and crystal 20MHz , for the code :
setup_timer_2(T2_DIV_BY_1,255, 1) , I only get 20KHZ pwm frequency.
So how can I set to its max frequency ??????

[Ttelmah]

There is a balancing 'act', between the output frequency, and the available resolution steps. You code gives the maximum frequency, _supporting 1024 steps in the output_.
If you think about it, since the PWM 'steps' in single counts of the crystal, this will give:

20000000/1024 = 19531.25Hz

To go faster, you have to sacrifice accuracy. So for a PWM, supporting just ten steps say, you can get 2MHz as your output. The actual maximum, would be a PWM with:

setup_timer_2(T2_DIV_BY_1,0, 1);

giving just four counts of the master clock, per pulse (2.5MHz). However you only get 2bits of output resolution.

You need to decide on what PWM frequency you need, and then see if enough resolution will be available at this frequency. So if (for instance), you want 100000Hz, then this would be the master clock over 200, giving 200 possible output steps, and using:

setup_timer_2(T2_DIV_BY_1,49, 1);

wth allowable 'duty cycle' numbers from 0 to 199.

Best Wishes

[PCM programmer]

Also see this thread for the PWM frequency formula:
http://www.ccsinfo.com/forum/viewtopic.php?t=17993

Related topics:
http://www.ccsinfo.com/forum/viewtopic.php?p=99719