[time-nuts] Clocking a PIC16F628A from a Rubidium Standard
attila at kinali.ch
Fri Nov 25 03:11:04 EST 2011
On Thu, 24 Nov 2011 09:37:33 -0700
Robert Darlington <rdarlington at gmail.com> wrote:
> I've done this but don't remember the detail on the wiring. The data sheet
> made it clear though. One thing I did notice is that the oscillator
> seemed to power the chip! If I were doing it again I'd probably use some
> kind of powered buffer on the oscillator input so that when I power down
> the circuit it actually stops.
This is why i mentioned the DC block capacitor. Even if you use a buffer,
you would still power the PIC. The path in this case are the protection
diodes on the input pin. By providing there an input voltage, you drive
the upper diode which conducts the "power" to the VDD line which in turn
powers the PIC.
If you use a buffer, you get still the protection diodes and thus still
the path to power the PIC (and the buffer).
Why does it take years to find the answers to
the questions one should have asked long ago?
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