TrueTime VME-SG2 560-5608, Manual

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When time from the GPS Engine is valid the front panel LOCK LED will blink slowly (2
second rate) until the phase errors are less than 10 microseconds. At that time the
LOCK LED will blink faster (twice per second) until the generator is phase locked to < 1
microsecond and the oscillator frequency has stabilized. At that time the LOCK LED will
be ON continuously. When time from the GPS Engine is not valid the LOCK LED will be
OFF. If the GPS Engine is not operating properly the red LED indicator on the front
panel identified as ERR illuminates. This LED may illuminate momentarily when power
is applied to the card or when the operational mode is changed. See Table 2-1 .
2.4.3 CODE SYCHRONIZED GENERATOR
The Code Synchronized Generator mode operates as a Generator that is synchronized
to an external IRIG B input code. The VME-SG-GPS card will operate with either IRIG B
amplitude modulated or IRIG B DC shift at RS-422 logic levels. The code input format
selection is made via Configuration register 2, bit 3. The Sync-Gen will phase lock to
the input code and discipline the VCTCXO. The phase correction logic advances or
retards the time to keep it phase locked to the IRIG reference. The Generator time is
phase shifted by 100 nanoseconds steps. The front panel LOCK LED indicator operates
in the same manner as in the GPS Synchronized Generator mode indicating relative
phase accuracy. See table 2-1. An ERR LED indicator on the front panel illuminates
when the input code is not present, is of the wrong format or fails to pass numerous
error detection criteria.
2.4.4 FRONT PANEL INDICATORS AND DISPLAY
LED INDICATORS - The VME-SG-GPS front panel has four indicator LEDs. They are
labeled POWER, 1PPS, LOCK and ERR. The POWER indicator is on when power is
applied to the card. The 1PPS indicator will blink once per second when the generator
is running. The LOCK and ERR indicators are only used in the synchronized generator
modes. The table below and sections 2.4.3 and 2.4.2 describe their operation.
LED
NAME CONDITION DEFINITION
LOCK Blinking Slowly Phase Error> 10 microseconds
Blinks Twice/sec Phase Error < 10 microseconds
ON Constantly Phase Error within spec
OFF Constantly Reference not valid
ERR ON Constantly Reference failure
OFF Constantly Reference is OK
Table 2-1, Front Panel LEDs
ALPHANUMERIC DISPLAY - An optional alphanumeric LED display is available that
consists of 4 lines by 4 characters. The display allows the user to observe time, date,
operational mode, sync status, position, satellite tracking status and self test results. A
switch on the front panel is used to select the different displays. The time display will
flash after power up in the GPS Sync-generator mode until LOCK has occurred. This
indicates that the time is not accurate.
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