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    Configuring PTP Grandmaster Clock Using External GPS Receiver

    For an ACX series router to act as a PTP grandmaster clock, the router needs to receive the timing information from an external GPS receiver. Typically, a GPS receiver would have a frequency output of 10-MHz, phase output of 1 pulse-per-second (PPS), and time of day (TOD) output.

    To configure PTP grandmaster clock on ACX Series routers, you need to configure:

    • GPS frequency input (10-MHz)
    • Time of day input
    • Cable length compensation of 1 PPS (optional)
    • Arbitrary time scale knob (optional)
    • Downstream slaves

    Configuring the GPS Frequency Input

    You need to configure the ACX router to receive the 10-MHz clock input from a GPS receiver. You can use the following CLI command hierarchy to configure the ACX router to receive the 10-MHz clock input from a GPS receiver:

    [edit chassis]
    synchronization {network-option (option-1 | option-2);source {gps{priority number;quality-level (prc | prs |sec | smc | ssu-a | ssu-b | st2 | st3 | st3e | st4 | stu | tnc);}}}

    After you have configured the GPS frequency input, enter the commit command from configuration mode.

    Configuring the Time of Day Input

    For ACX to act as a PTP grandmaster clock, the router needs to know the current time. The GPS receivers recover precise time from the GPS or GLONASS satellites and typically sends that time out of a serial interface. The timing information is usually sent in the following formats:

    • An ASCII string containing DD-MM-YYYY, HH-MM-SS.

      Where DD – day of month, MM – Month, YYYY - Year, HH - Hour, MM - Minutes, SS - Seconds. The TOD information is in National Marine Electronics Association (NMEA) format, TCA6500’s calendar-based format.

    • An ASCII string containing time in atomic time (TAI) format. The TOD information is the TCA6500’s TAI-based format.
    • Binary format. The TOD information is in Trimble Standard Interface protocol (TSIP) based format. The TOD information is sent in report packets as a stream of bytes.

    Use the following CLI command hierarchy to configure TOD input in the ACX series routers:

    [edit chassis]
    synchronization {port auxiliary {client {time-of-day-format {ascii <format string>;}}}}

    The client specifies that the port on the ACX router receives signals from the external GPS receiver.

    The following is a sample configuration when time of day is received from a GPS receiver with TCA TAI format:

    [edit]
    user@host# show chassis synchronization
    port auxiliary {
        client {
            time-of-day-format {
                ascii " T%S%TAI%UU%P";
            }
        }
    }

    The following is a sample configuration when time of day is received from a GPS receiver with TCA calendar format:

    [edit]
    user@host# show chassis synchronization
    port auxiliary {
        client {
            time-of-day-format {
                ascii "C%S%hh%mm%ss%DD%MM%YYYY^ %UU%P";
            }
        }
    }

    Note: You need to configure the input TOD in ACX routers based on the TOD format received by the GPS receiver.

    Modified: 2017-02-02