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

Hans Holzach hans.holzach at gmail.com
Sat Jan 10 12:16:30 EST 2015


i have a prs-10, software version 3.15, serial number 5351. default lock 
mode is 1, default time offset is 0. the fc values have been written to 
the EEPROM twice in the last 20 hours. fc!? returns 233,1426,1640,1647.


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 
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 

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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