[time-nuts] Clocking a PIC16F628A from a Rubidium Standard

Robert Darlington rdarlington at gmail.com
Thu Nov 24 11:37:33 EST 2011


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.

-Bob

On Thu, Nov 24, 2011 at 7:50 AM, Attila Kinali <attila at kinali.ch> wrote:

> On Thu, 24 Nov 2011 14:41:24 +0000
> Stephen Farthing <squirrox at gmail.com> wrote:
>
> > I have an Efratom 101 frequency standard with a 10 MHz TTL otput. I want
> to
> > use this to clock a PIC 16F628A so I can make a frequency counter with a
> > resolution of 1 Hz. I am going to use the design by EI9GQ here
> > http://homepage.eircom.net/~ei9gq/counter.html . What I need to know is
> how
> > i should go about electronically interfacing the TTL output from the
> > rubidium standard so that it can clock the PIC. Has anyone on the list
> > actually done this successfully?
>
> Have a look at the PIC 16F628 data sheet, it will tell you the requirements
> for the clock input and there should be circuit for external clock signal
> listed. If it's not in the datasheet, it should be in an appnote.
>
> Usually, chips accept sinusoidal and rectangular inputs up to 0V-VDD swing.
> If i'm reading the schematic correctly and the PIC runs with 5V, then
> you should be able to just feed the Efratom output directly to the PIC.
> Maybe, a ceramic 100n capacitor in this line should be used to do
> a DC isolation (1u cermaic should do as well).
>
>                        Attila Kinali
>
> --
> The trouble with you, Shev, is you don't say anything until you've saved
> up a whole truckload of damned heavy brick arguments and then you dump
> them all out and never look at the bleeding body mangled beneath the heap
>                -- Tirin, The Dispossessed, U. Le Guin
>
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