Microchip Technology GPS-2700, Руководство пользователя

Страница: 40 / 77

GPS-2700 User’s Guide
DS50003016A-page 40

2020 Microchip Technology Inc.
3.3.20 GPS:REF:ADEL <float> <s | ns > [-32767ns,32767ns]
The ADELay command allows bi-directional shifting of the 1PPS output in relation to
the UTC 1PPS reference in one nanosecond steps. This allows antenna cable delay
compensation, as well as retarding or advancing the 1PPS pulse arbitrarily. Typical
antenna delays for a 30 foot antenna cable with 1.5
ns per foot propagation delay would
be compensated with the following command:
GPS:REF:ADEL 45ns
This command can be used to fine-tune different units to have co-incident 1PPS pulse
outputs. Please note that during normal operation the 1PPS pulse may wander around
the UTC 1PPS pulse while the unit is tracking the GNSS signals. The present offset
between the 1PPS output and the UTC 1PPS signal can be queried with the command
SYNC:TINT? and this offset should be taken into account when calibrating two unit’s
1PPS outputs to each other, because the lock algorithms will try to steer the CSAC for
a 0.0
ns offset to the UTC 1PPS time-pulse.
3.3.21 GPS:REF:PUL:SAW?
This command returns the momentary sawtooth correction factor that the GNSS
receiver indicated.
3.3.22 GPS:RESET ONCE
Issues a reset to the internal GNSS receiver. This can be helpful when changing the
antenna for example, since the GNSS receiver measures the antenna system’s C/No
right after reset, and adjusts its internal antenna amplifier gains accordingly. It takes
approximately 1 minute for locking to commence after a GPS reset, as indicated by the
red blinking LED.
3.3.23 GPS:TMOD <ON | OFF | RSTSURV>
This command selects the Timing Mode of the GNSS receiver.
If the Timing Mode is OFF, the receiver will act as a regular GNSS receiver. This mode
has to be chosen if the unit is mobile.
If the Timing Mode in ON, the timing features of the GNSS receiver are enabled. At
power-up, the Hold position stored in NV memory will be sent to the GNSS receiver and
will be used as the reference. In order to use this mode, the receiver position must be
known as exactly as possible. Errors in the Hold position will translate into time errors
depending on the satellite constellation.
The Hold position can be set manually by the user or can be the result of a Survey exe-
cuted by the GNSS receiver.
If the Timing Mode is RSTSURV, the GNSS receiver will start a Survey every time the
unit is powered-on and following the Survey, the GNSS receiver will run with the timing
features enabled.
3.3.24 GPS:SURV ONCE
This command starts a Survey. At the end of the Survey, the calculated Hold position
will be stored in NV memory. The Survey parameters can be set with the command
GPS:SURV:DUR and GPS:SURV:VAR.
3.3.25 GPS:SURV:DUR <sec>
This command sets the Survey minimal duration.