Not 100% certain about the ceramic resonators, but I do know that the 
new PIC18f26J50's claim to have an accurate enough intosc to be able to 
do away with any external oscillator at all.

The datasheets often will discuss the clock accuracy needed, IIRC.   
Look in the oscillator section and also in the USB section of the datasheet.

-forrest

Peter van Hoof wrote:
> 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