Em 23/3/2012 18:55, IVP escreveu:
>> With Fosc =3D 48MHz
> The OP said the PICDEM FSUSB has a 20MHz crystal. I'm not
> familiar with that board. Can it be changed to 48MHz ?

The PIC18F4550 and siblings have a PLL with a prescaler. The input to
the PLL must always be 4MHz and its output is always 96MHz.
Certainly he is dividing the 20MHz by 5 to get the correct input of 4MHz
to the PLL.

The PLL output is routed to a divider by 2 to clock the USB peripheral
and can also be routed to another divider by 2, 3, 4 or 6 to clock the CPU.


Isaac
--=20
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