Tapping onto the Oscillator
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I would like to use the Stamp II's built in 20MHz oscillator as a clock
source for other external circuitry. Is this possible (i.e., has any one
done it) and is it reliable (i.e., does it affect the Stamp's operation)? I
realize a ceramic resonator is not the most accurate clock source, but I
believe it is accurate enough for my application. Any comments on this are
appreciated.
--
Greg
source for other external circuitry. Is this possible (i.e., has any one
done it) and is it reliable (i.e., does it affect the Stamp's operation)? I
realize a ceramic resonator is not the most accurate clock source, but I
believe it is accurate enough for my application. Any comments on this are
appreciated.
--
Greg
Comments
A few hints... I strongly suggest using a fast CMOS gate or inverter to
buffer the 20MHz clock output before doing anything else with it. Keep your
hookups real short! If you have to go more than a few inches, add a series
resistor of about 33 ohms at your buffer output to suppress ringing. Buffer
input capacitance will probably shift your operating frequency slightly...
There's not much you can do about it, because the ceramic resonator in the
BS2 is integrated with its load capacitors. If oscillation stops or becomes
unreliable, try a discrete JFET buffer (source follower). To check for
unreliable oscillation, reduce the operating voltage temporarily (bypass
the BS2's on-board regulator to make this test).
>I would like to use the Stamp II's built in 20MHz oscillator as a clock
>source for other external circuitry. Is this possible (i.e., has any one
>done it) and is it reliable (i.e., does it affect the Stamp's operation)? I
>realize a ceramic resonator is not the most accurate clock source, but I
>believe it is accurate enough for my application. Any comments on this are
>appreciated.
Mike Hardwick, for Decade Engineering -- <http://www.decadenet.com>
Manufacturer of the famous BOB-II Serial Video Text Display Module!