TrueTime 151-602 - 3-172 KEYPAD FUNCTION 72 - FAULT STATUS REQUEST

X
X
L
L
D
D
C
C
M
M
A
A
N
N
.
.
d
d
o
o
c
c
3
3
-
-
3
3
1
1
R
R
E
E
V
V
E
E
"Oscillator phase" is the instantaneous error between the XL-DC timing outputs and GPS. Press
"FUNC/ENTR" "7" "1" and the display will show:
Osc Phase
-5.788e-09 s
indicating that the XL-DC timing was most recently reported to be approximately 6 nanoseconds late.
This number has the full effects of Selective Availability superimposed upon it. The oscillator control
loop servos the mean of this number to zero.
"Oscillator offset" is the frequency offset or error with respect to the GPS frequency. Press
"FUNC/ENTR" and the display will show:
Osc Offset
-2.150e-11
indicating that the internal or external oscillator frequency is less than GPS by approximately 2 parts in
10
-11
.
"Oscillator drift" is the change in oscillator frequency per day. Press "FUNC/ENTR" again and the
display will show:
Osc Drift
3.990e-12/DAY
indicating that the internal or external oscillator frequency is changing positively with respect to GPS by
approximately 4 parts in 10
-12
per day.
"Oscillator DAC" is the signed 16 bit DAC control integer which sets the DAC output voltage to control
the internal or external oscillator. Press "FUNC/ENTR" again to display:
DAC
16368
indicating that the DAC output voltage is at either +2.5 V or +7.5 V depending upon whether the GPS-
XL Module’s DAC range setting jumper JP5 is off or on, respectively.
3-172 KEYPAD FUNCTION 72 - FAULT STATUS REQUEST
Keypad Function 72 displays the status of certain fault detectors within the XL-DC. These are currently
limited to the status of the Antenna feed circuit, the PLL synthesizer lock status and GPS lock status.
Press “FUNC/ENTR", "7","2" and the display will show:
Fault Status
Antenna: XXX