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Crystal selection for PIC24F series

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osmosis321:
Wow, the 24F series can run at up to 32MHz, all I need to do is get a crystal that runs at that frequency and Bob will be my uncle.  Or so I thought.

When I scoped it, the signal was only 10.6667MHz, and when I read the fine print on the crystal datasheet, wouldn't you know it, 32MHz is the third harmonic.

I know what that means but I don't know what I need to do to get it to operate at full frequency.  The easiest thing to do would be to get a different crystal, but will it really be that simple..?

Zero999:
Assuming you're using a 32MHz crystal this is pretty common. Adjusting the loading capacitance or being more careful with the layout might help.

tecman:
Use an 8 Mhz xtal and the internal PLL to get 32 Mhz.

paul

osmosis321:

--- Quote from: tecman on February 09, 2011, 05:16:37 am ---Use an 8 Mhz xtal and the internal PLL to get 32 Mhz.
--- End quote ---

It can't be that easy..  but I'll try it anyway.

alexh:
As tecman said you can perfectly use for example an 8 MHz crystal (or for that matter a 4, 12, 20MHz, ...). You just need to adjust the PLLDIV. You could even use the 8MHz internal oscillator block; thanks to the PLL you can generate all the required frequencies from that.

Regards,
Alex

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