[time-nuts] FE-5680A decoded - another piece of the puzzle
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.
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
> 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.
> Skip Withrow
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