[time-nuts] TDS12 (AKA PRS10) use indication.

Mike Cook michael.cook at sfr.fr
Wed Jan 7 13:40:56 EST 2015

I have a SR TDS12 which apart from name appears to be a PRS10. The ID string indicates PRS10 and the firmware version is the same as on another PRS10 that I have. The only differences that I could see at first power up is the that default config has Lock Mode 2 as opposed to the normal default of 1, and a zero time offset. As I didn’t get my PRS10 new, I do not know if that is normally calibrated when new. Anyhow, it works a charm with unlocked frequency stability in spec. It has a date code of 03 2004 and that and the S/N are newer than the PRS10. Both have firmware version 3.24.

The user manual indicates that the FC!? command returns a power cycle count and EEPROM update count in addition to the frequency control values.

"The FC!? Command may be used to read the value which is stored in the EEPROM. The value stored
in EEPROM is used to set the 10 MHz at startup, before the FLL can be established.
Occasionally while the unit is operating (at about 20 minutes after power-on and once a day
there after) the program will write a new value to EEPROM to correct the value for crystal
aging. Example: FC!? will return four values (separated by commas), the number of power
cycles the unit has undergone, the number of times the FC pair has been written to EEPROM,
and the value of the FC pair (high, low) which is used at turn-on and restart."

The same text is in the user manuals V1.1 to the latest, v1.4.

I had only just noticed this as while I was finding out how to set the TO value. So I used the count to calculate a rough powered on time. It came to about 12 years which although longish is well within the expected lifetime. I started to track it and found that it is not updated daily as per the manual, but systemtically twice a day.  That of course halves the usage time. Unfortunately I have not been able yet to see what my PRS10’s values are as I am still fiddling with the TDS12.  


Can anyone with PRS10s on the bench tell me if they see the same behavior ?


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