On 07/30/11 10:24 am, Oliver Seitz wrote:

I'm no USB expert, but I know that USB does have quite strict timing.

Wikipedia says: Clock tolerance is 480.00 Mbit/s ą500 ppm
<http://en.wikipedia.org/wiki/Parts_per_million>, 12.000 Mbit/s ą2500
ppm, 1.50 Mbit/s ą15000 ppm.

If I'm converting it right, that's 0,05% for 480MBit/s, 0,25% for
12MBit/s and 1,5% for 1.5Mbit/s.

So full speed USB requires a pretty accurate crystal (or is that a 'normal' accuracy for ordinary crystals?).

Regards, Rob.

--
R. Hamerling, Netherlands --- http://www.robh.nl

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