ZED-F9T - Integration Manual
value "rolls over" back to zero. Consequently, GPS L1 receivers can't tell the difference between, for
example, 1980, 1999 or 2019 etc.
Fortunately, although BeiDou and Galileo have similar representations of time, they transmit
sufficient bits for the week number to be unambiguous for the foreseeable future (the first
ambiguity will be in 2078 for Galileo and not until 2163 for BeiDou). GLONASS has a different
structure, based on a time of day, but again transmits sufficient information to avoid any ambiguity
during the expected lifetime of the system (the first ambiguous date will be in 2124). Therefore, u-
blox 9 receivers using Protocol Version 24 and above regard the date information transmitted by
GLONASS, BeiDou and Galileo to be unambiguous and, where necessary, use this to resolve any
ambiguity in the GPS date.
Customers attaching u-blox receivers to simulators should be aware that GPS time is
referenced to 6th January 1980, GLONASS to 1st January 1996, Galileo to 22nd August
1999 and BeiDou to 1st January 2006; the receiver cannot be expected to work reliably with
signals that appear to come from before these dates.
3.5.9.1 GPS-only date resolution
In circumstances where only GPS L1C/A signals are available and for receivers with earlier firmware
versions, the receiver establishes the date by assuming that all week numbers must be at least
as large as a reference rollover week number. This reference rollover week number is hard-coded
at compile time and is normally set a few weeks before the software is completed, but it can be
overridden by CFG-NAVSPG-WKNROLLOVER configuration item to any value the user wishes.
The following example illustrates how this works: Assume that the reference rollover week number
set in the firmware at compile time is 1524 (which corresponds to a week in calendar year 2009,
but would be transmitted by the satellites as 500). In this case, if the receiver sees transmissions
containing week numbers in the range 500 ... 1023, these will be interpreted as week numbers
1524 ... 2047 (calendar year 2009 ... 2019), whereas transmissions with week numbers from 0 to
499 are interpreted as week numbers 2048 ... 2547 (calendar year 2019 ... 2028).
It is important to set the reference rollover week number appropriately when supplying u-
blox receivers with simulated signals, especially when the scenarios are in the past.
3.6 Timing functionality
The ZED-F9T provides precision time references used by remote or distributed wireless
communication, industrial, financial, and power distribution equipment.
3.6.1 Time pulse
3.6.1.1 Introduction
The ZED-F9T receiver includes two time pulse outputs with configurable duration and frequency.
The time pulse function can be configured using the CFG-TP-* configuration group for the desired
time pulse; TP1 or TP2. Note that TP1 refers to pin 53 (Timepulse) and TP2 to pin 54 (Timepulse
2). The UBX-TIM-TP message provides time information for the next pulse, time source and the
quantization error of the output pin.
UBX-19005590 - R01
3 Receiver functionality
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