Matthias,
I'm working on the same project. It looks like you should only be able to get
the difference between the two 1pps signals out of the rs-232 port. Maybe
Heather can display it?
This is from the X72 designers reference manual
"A 1 PPS output is an integral part of the design.An optional 1 PPS input
allows the unit to track aGPS or other external reference, and display
thedifference between the input and the 1 PPS generatedby the X72 through the
RS232 link."
"3.4.2 X72 1 PPS Input and OutputThe 1 PPS output signal of the X72 unit is
positive edge triggered and gated with the rising edge ofthe clock. It’s
duration for a 10 MHz unit is 400 ns ±10%. Rise/fall time is 4 ns.The 1 PPS is
exactly divided from the XO frequency.Future implementation will support
tracking, synching and smoothing of incoming 1 PPS toproduce the output 1 PPS."
Stephan
On Sunday, March 4, 2018 6:47 AM, Matthias Jelen <[email protected]>
wrote:
Hi Mark,
thanks for your reply.
> Try enabling the PPS input form the "P menu.
I can´t find this option - I can toggle the PPS output, but
not the input.
BTW, what´s the "set TIC" option? I can enter a number here,
but I can´t find something about this command in the manual...
&a Auto-Tune seems to work well - I see the plot stepping
and a slope is calculated.
What´s the expected behaviour if I go to d-e: "Enable HW
discipline" ? I can´t see any changes here.
I checked the SA.22.C manual as well, but this contains more
or less the same information as the X72.
Regards,
Matthias
> Also, to verify that it is using the PPS input try the &a auto-tune command.
> It will set the TIC and DDS tune word to to 0, collect data for for however
> long you requested (an hour is a good start), then calculate the drift rate
> and set the DDS tune word to put the device on frequency. The EE command
> should set save the DDS word in EEPROM. If the unit is seeing the PPS
> input, you should see the PPS plot stepping as the DDS freq drifts.
>
> Many of the X72 settings cannot be read back from the unit. Heather
> maintains a "software eeprom" with the settings that it knows about in the
> file "tbeeprom.dat". Until you update a setting, what is displayed for that
> setting may not be correct. Use the "P" menu to set each of the settings so
> that Heather can learn what they are. When Heather starts up, it restores
> all the last settings from the file.
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