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20ms Period on PWM using 10MHz clock

 
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thurmanc
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20ms Period on PWM using 10MHz clock
PostPosted: Sat Mar 14, 2009 10:34 pm     Reply with quote
Is there any way to produce a 20ms period for the PWM output of a PIC 16f877a using an input clock of anywhere between 2MHz - 20MHz? I can use hardware to move the oscillator clock to anywhere in this range so the lowest I can go is 2MHz.
PCM programmer



Joined: 06 Sep 2003
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PostPosted: Sat Mar 14, 2009 11:07 pm     Reply with quote
This post has the pwm frequency formula:
http://www.ccsinfo.com/forum/viewtopic.php?t=17993&start=1
For a 2 MHz oscillator, the lowest you can go is 122 Hz.

To get a 50 Hz pwm frequency, you need to do software PWM.
See the sample code I posted in this thread, and also the links.
http://www.ccsinfo.com/forum/viewtopic.php?t=37807
thurmanc
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PostPosted: Sat Mar 14, 2009 11:49 pm     Reply with quote
Thanks so much for your help. I see I may have a resolution problem using your code but it is much better than not having it work at all Smile
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