PPS State Value Action Performed by SA.22c
PDATEDDSSTATE 8 Update SA.22c DDS based on PIDCALCSTATE output
ALCSLOPESTATE 9 Calculate slope of incoming 1PPS vs. SA.22c 1PPS during holdover
For more information on 1PPS states, see .1PPS Algorithm Theory of Operation (see page 36)
7.6.4 The g Command
The g command helps to toggle the operation of the SA.22c in any of the three modes mentioned
below, which affect the output of the lock pin (pin 14 see Note 10 in ). The g Command (see page 34)
This 1PPS mode can be changed but cannot be saved. If power is cycled to the unit, it reverts to the
factory default. The following are the modes of operation:
0 = 1PPS disciplining disabled—Normal rubidium lock pin functionality. Only the rubidium loop
needs to be locked to indicate a locked condition on pin 14.
1 = 1PPS disciplining enabled—Normal lock pin functionality. Only the rubidium loop needs to be
locked to indicate a locked condition on pin 14.
2 = 1PPS disciplining enabled—Requires both rubidium loop to be locked and 1PPS synchronization
lock to indicate a locked condition on pin 14.
There are two types of 1PPS customer firmware. The 1PPS standard firmware provides an Rb or Rb/1PPS
lock indicator at pin 14 and a service indicator on pin 12 of the SA.22c I/O connector. The 1PPS LED
firmware uses the same functions for pin 14, but pin 12 is reserved for 1PPS lock indication only. There
is no service pin on the 1PPS LED versions. The factory default modes set by the g command for each
firmware version are:
1PPS standard firmware—Mode 2. Rb lock and 1PPS lock indicated on pin 14.
1PPS LED firmware—Mode 1. Rb lock only indicated on pin 14 and 1PPS lock indicated on pin 12.
The key sequence to change the output/lock indicator mode with the g command is as follows:
At the r> prompt, type g, then type either 0, 1, or 2 depending on the desired output mode, and press
Enter.
Note: 1 These numbers are in HEX format.
Note: 2 1PPS states: 0 to 2—Initialize; 3, 9—Holdover; 6 to 8—Disciplining.
Note: 3 When connecting to a GPS receiver, the factory default mode is recommended. Start with y1=1
(DF) and Y2=400 TC in seconds). These values work well for most GPS receivers.
Note: 4 Use z command to save your settings.
Note: 5 SA.22c Rubidium system locks approximately 5 minutes after startup.
Note: 6 SA.22c initial frequency must be less than ±3PPB for 1PPS to lock.
Note: 7 Initial 1PPS lock occurs between 3 and 5 minutes after both lock and valid 1PPS are present.
Note: 8 Confirm the firmware version by issuing the i command.
Note: 9 xx is a value returned, which is the hex equivalent of the number of times the table has been
written to. TData can be either 1 or 2.
Note: 10 If the J2 Molex connector is used on the adapter test board, then the lock pin is 21 and the
service pin is 8.
Note: 11 If the lock and service voltages are measured on the adapter test board, then the lock signal is
on TP1 and the service signal is on TP3.
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