[time-nuts] FE-5680A decoded - another piece of the puzzle

paul swed paulswedb at gmail.com
Mon Jan 30 09:51:47 EST 2012


Skip previously in these threads there was a direct real analog control
that was discovered.
I have used it and it works well. The thread describes how to get to it.
Regards
Paul

On Sun, Jan 29, 2012 at 11:22 PM, Skip Withrow <skip.withrow at gmail.com>wrote:

> Hello Nuts,
>
> I've been trying to get the analog EFC to work on the FE-5650A (a very
> close cousin of the FE-5680A).  On these oscillators it is normally on
> pin-8 of the DB-9 (Option 12 and 30).  As one of the serial lines is on
> this pin, I traced the jumper that is placed for the EFC option(s).
> However, changing the voltage on the pin does not seem to move the
> frequency (or at least not very much if it does). Anybody know the nominal
> EFC sensitivity of the 5680?
>
> On tracing things further, I have found that this input goes into the (4
> channel) A/D associated with the microproccesor.  Changing the voltage
> gives a value in message 5A that also changes a corresponding amount.  The
> EFC bytes are bytes 5 & 6 of the 5A message, first byte is low second byte
> is high.  Appears to be 12-bit value (0FFF max).
>
> The question is - how do you enable the EFC?  Maybe it is a bit that has to
> be set in one of the other messages. (But then how does the uP communicate
> the EFC value to the physics package?)  It (more likely) may be that I have
> not found the true C-field control circuitry yet and the A/D is just a
> monitor.
>
> I recall someone implementing C-field control on a FE-5680A with the pot
> disabled, but cannot find it now.  If someone can point me to that post I
> sure would appreciate it.
>
> Thanks in advance.
>
> Regards,
> Skip Withrow
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