[time-nuts] Setting up PRS10 with M12+T GPS

[Magnus Danielson]

Björn,

On 05/03/2012 12:30 AM, bg at lysator.liu.se wrote:
> Magnus,
>>>
>>> Tbolt       PRS10A     PRS10B
>>> 1pps  -->     PPSIN
>>>               PPSOUT -->   PPS IN
>>>
>>> PRS10A slowly following the Tbolt (PRS10A PT8)
>>> PRS10B "quickly" following the PRS10A (PRS10B PT0)
>>>
>>> Ok?
>>
>> Yes, but if this is a free-running thunderbolt (I think you said
>> something about that) then PT8 will be a bit slow. For a tracking
>> thunderbolt PT8 may work, even if it takes time for it to track in.
>
> No a GPS locked Tbolt.

Thanks for that clarification, I am obviously a bit tired.

> A free-running Tbolt was just an example of a very
> low noise 1PPS source, where I would find it useful to have a "PT-1" bias
> calibration mode bypassing the PLL, and moving the PPSOUT directly with
> the PPSIN.

So this does not suffice?:

Page 33:
"When provided with an accurate and stable 1pps source, the unit will 
automatically align its 1pps output to the 1pps input and then adjust 
the frequency of the rubidium reference to maintain the alignment over 
time."

Page 17:
"After receiving 256 consecutive "good" 1pps inputs, the 1pps pulse 
delay is set to the last of the 256 time-tag values."

I interpret this as this:

When the 256s PPS has been approved, the last-time-tag is used to adjust 
the output delay such that the output signal is aligned, within the 
precision of the time-offset value.

Then, the PLL is running. Either the output delay is not shifted and 
only the PPS alignment is done on approval, or it is updated in the 
background. The text only supports the former explicitly, but it would 
be nice to verify if it is either of these.

Doing phase-jump of PPS like this on start-up is expected. I've even has 
a measurement on it somewhere.

Cheers,
Magnus