[time-nuts] Rb Oscillator - rather fundamental question
matt at smiffytech.com
Wed Feb 24 08:45:08 UTC 2010
Quoth Kasper Pedersen at 24/02/10 17:44...
> It will.
> Set the fuses as you would have for a 10MHz crystal, and capacitively
> couple the source to XTAL1. Leave XTAL2 open.
> Do not set the fuses for 'external clock mode'.
> Do put something like 100pF+1k Ohm in series with the input. While they
> won't promise anything, I have deliberately run 1A into the protection
> diodes of an ATMega16 for many seconds and still had a functional part.
Many thanks. I was wondering about doing this; Chris Keuthe quoted the
figures from the datasheet but then I thought that this would be the
ratings for an external oscillator, as surely an actual crystal would be
putting out a much smaller voltage than those quoted. A few days ago,
on another list, David had suggested something similar with "faking" a
crystal for an AT90S8535 RTC.
I also wondered how an AVR could not work when PICs are reported to.
I will certainly use the series R+C as you and David have suggested, but
will not worry about further protection - the AVR is one of the cheapest
components in the whole system - I am far more concerned about damaging
the Rb module than the AVR!
Thanks to all who have answered on this. I will post a link to details
when I get this project up and running.
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