RuggedCom RuggedRouter RX1100 - Manual (Page 269)

32. Configuring IRIGB And IEEE1588
Revision 1.14.3 269 RX1000/RX1100™
PTP Identifier Descrption
NTP The PTP clock is a secondary reference standard clock. The router uses this identifier when
it has synchronized with remote NTP server.
DFLT After the router has power cycled but before any GPS or NTP locks have occurred.
PTP favors preferred masters over normal masters, GPS over NTP over DFLT, higher clock stability
over lower clock stability.
32.1.1.3. Synchronizing NTP from IEEE1588
If GPS is unavailable and PTP becomes a slave the NTP server will view the received IEEE1588
time as any other source of time. The quality (i.e. stratum) of IEEE1588 information is determined
by the type of clock source at the master, the number of Boundary Clock hops and the measured
network jitter.
The number of Boundary Clock hops is the number of IEEE1588 devices the original time source is
relayed through (and not Ethernet hops) and is always 1 or higher.
The measured network jitter factor is 0 if jitter is higher than 1 microsecond and -1 if less than 1
microsecond.
PTP Identifier Stratum reported to NTP
GPS 1 + Number of Hops ? 1 (if low jitter)
NTP user configurable value (default 2) + Number of Hops ? 1 (if low jitter)
DFLT user configurable value (default 10) + Number of Hops ? 1 (if low jitter)
The stratum number reported will be limited to a range of 1 to 16 to comply with NTP.
As an example, a directly connected PTP clock having a GPS clock source and low jitter would report
a stratum of 1. With defaults a 2 hop away PTP clock having a NTP clock source and high jitter would
report a stratum of 4.
32.1.2. IRIGB Fundamentals
IRIGB outputs are provided by the Precision Time Protocol Card option.
The Inter-Range Instrumentation Group (IRIG) IRIG-B standard details the format of an output signal
containing information for the current day, hour, minute and second in UTC format, broadcast at
the start of each second. The RuggedRouter complies to IRIG Standard 200-04 generating formats
IRIGB002 and IRIGB003 (PWM) and IRIGB122 and IRIGB123 (AM).
32.1.2.1. IRIGB Output Formats
The router provides three ports by which the signal is distributed, namely:
• An Amplitude Modulated (AM) sinusoidal output port (PTP1),
• Two TTL voltage level output ports (PTP2 and PTP3) which may be configured as either pulse
per second (PPS) or pulse width modulated (PWM).
The signal can be used to synchronize intelligent devices to a high quality time source, called the
reference clock. The router uses a global positioning satellite (GPS) receiver, NTP or the router's local
clock as the reference clock.