Trimble Outdoors THUNDERBOLT 64057-00-ENG User Manual
Page 82
A Trimble Standard Interface Protocol
80 Trimble ThunderBolt E GPS Disciplined Clock User Guide
the accurate position the receiver is using to perform time-only fixes. When the self-
survey is disabled or otherwise inactive and the receiver is using a position fix
operating mode, then the position sent is the position fix computed on the last second.
Data field
Description
Receiver Mode
This field shows the fix mode that the GPS receiver is currently configured for. The
receiver spends most of its time in the Over-Determined Clock Mode where it uses all
available satellites to perform the best time-only fix possible. See packet 0xBB for a
description of all available receiver modes.
Self-Survey Progress
When a self-survey procedure is in progress, this field shows the progress of the survey as
a percentage of fixes collected so far. The self-survey will be complete when the self-
survey progress reaches 100 percent. This field only has meaning while a self-survey is in
progress.
Holdover Duration
When in the Manual or Auto Holdover state, this field shows the amount of time spent in
holdover in seconds. When the unit is not in a holdover state, this field shows the amount
of time the receiver spent the last time it was in a holdover state.
Critical Alarms
This field is bitwise encoded with critical alarms indicators. A critical alarm indicates a
condition that would tend to severely impair the function of the receiver. For each bit, a
value of 0 means that the condition is not indicated. Bits not described below should be
ignored.
Bit4: When 1, indicates that the oscillator control voltage is at a rail. If this condition
persists then the Min-T can no longer bring the frequency of the oscillator into alignment
with GPS and is most likely in need of a new oscillator. This condition should not occur
within 15 years of operation.
Minor Alarms
This field is bitwise encoded with several minor alarm indicators. A minor alarm indicates
a condition that the user should be alerted to, but does not indicate an immediate (or
necessarily any) impairment of functionality. For each bit, a value of 0 means that the
condition is not indicated. Bits not described below should be ignored.
•
Bit 0: When 1, indicates that the oscillator control voltage is near a rail. If this
condition persists, then the oscillator is within 2 years of becoming untunable, at
which point the unit will need a new oscillator. This condition should not occur for at
least 12 years of use and is a result of oscillator crystal aging.
•
Bit 1: When 1, indicates that the antenna input connection is open. More precisely,
this bit indicates that the antenna input is not drawing sufficient current. Normally,
The receiver provides power to the antenna's LNA (Low Noise Amplifier) through the
center conductor of the antenna cable. On-board circuitry senses this current draw,
and if low, this condition will be indicated. However, when the antenna is powered
elsewhere (e.g., when using a splitter) then an antenna open condition is expected
and does not imply a fault nor does it impair the operation of the receiver.
•
Bit 2: When 1, indicates that the antenna input is shorted. More precisely, this bit
indicates that the antenna input is drawing too much current. On-board protection
circuitry prevents any damage to The receiver when its antenna input is shorted to
ground. This condition tends to indicates a fault in either the antenna cable or the
antenna itself.
•
Bit 3: When 1, indicates that no satellites are usable. In order for a satellite to be
usable, it must be tracked long enough to obtain ephemeris and health data.
•
Bit 4: When 1, indicates that the oscillator is not being disciplined to GPS. Before the
Mini- T can begin disciplining the oscillator, it must begin receiving information from
the GPS receiver. This occurs any time that the receiver is performing fixes.
•
Bit 5: When 1, indicates that a self-survey procedure is in progress.
•
Bit 6: When 1, indicates that there is no accurate position stored in flash ROM.
•
Bit 7: When 1, indicates that the GPS system has alerted the receiver that a leap
second transition is pending.