I use a 20MHz Quartz Crystal with a 4550 for USB in one of my projects


This works fine with these settings:

_PLLDIV_5_1L = divide by 5
_CPUDIV_OSC1_PLL2_1L = primary oscilator used directly for system clock
_USBDIV_2_1L = USB clock from 96 MHz pll divided by 2
_FOSC_HS_1H = HS oscilator

Peter



----- Original Message ----
> From: Bob Ammerman <rammerman@verizon.net>
> To: Microcontroller discussion list - Public. <piclist@mit.edu>
> Sent: Wed, October 28, 2009 11:00:26 PM
> Subject: Re: [PIC] 18F4550 resonator for USB?
> 
> Haven't looked at it for some time, but doesn't he need to use a 6MHz XTAL 
> with PLL to do USB? Or a 24MHz XTAL, I guess.
> 
> 20 MHz won't work because the USB SIE requires a 24MHz clock, IIRC.
> 
> -- Bob Ammerman
> 
> ----- Original Message ----- 
> From: "Peter van Hoof" 
> To: 
> Sent: Wednesday, October 28, 2009 9:58 PM
> Subject: [PIC] 18F4550 resonator for USB?
> 
> 
> > Greetings to all.
> >
> > A friend has started building a circuit with a 18F4550 and a 20 MHz 3 pin 
> > ceramic resonator.
> > Is a resonator accurate enough to allow USB communication or does he need 
> > a quartz?
> >
> >
> > Peter van Hoof
> >
> >
> >
> >
> > -- 
> > http://www.piclist.com PIC/SX FAQ & list archive
> > View/change your membership options at
> > http://mailman.mit.edu/mailman/listinfo/piclist 
> 
> -- 
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist



      
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist