Bob Ammerman wrote 2012-09-24 20:29:
>>> Fifteen new PICs with crystal-free USB operation.  Includes 16F varieti=
es
>>> down to 14 pins, 18F "replacements" for the venerable 4550 and 2550, an=
d
>>> larger 18F varieties.
>>
>> One blurb I read mentions that these chips only obtain 0.25% accuracy
>> when actively connected to USB.  Does this mean they are synchronizing
>> to the timebase in the USB host?
>
> My understanding is that this is true for the smaller chips.
>
> The 64/80/100 pin chips appear to have their own accurate clock.
>
> I could be wrong...
>
> -- Bob Ammerman
> RAm Systems
>

According to "TABLE 2-5: OSCILLATOR CONFIGURATION OPTIONS FOR
USB OPERATION" in the datasheet for the "PIC18F87J50 FAMILY":
http://ww1.microchip.com/downloads/en/DeviceDoc/39775c.pdf

all USB compatible oscillator settings uses EC (External clock)
or HS (High speed crystal), sometimes with PLL. So no fully
internal osciallator config in that case, at least.

Jan-Erik.

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