194 SyncServer 600 Series User’s Guide 098-00720-000 Revision D1 – February, 2018
Chapter 6 Provisioning
Provisioning Inputs with Manual Entry Controls
A simple example of this would be if the only available time input is an IRIG1344
and the S6xx is supporting a PTP (IEEE-1588) Master function. Since the IRIG
input provides UTC timescale and PTP uses TAI timescale, the S6xx must convert
from UTC time to get to TAI time. However, this conversion requires awareness of
the current accumulated leapseconds, information the IRIG input does not supply.
Without an auxiliary method for learning this value, the PTP output will encode the
Announce message with the ptpTimescale flag set to false, which means that PTP
clients using this S6xx PTP Master are unable to derive usable time. The remedy for
this scenario is for the user to provide the current conversion value, which is easily
known. By entering this in the “Manual Offset from TAI” field, the S6xx will now trust
this to be the correct conversion and will apply it when it is needed to support an
output. In the specific example, the time conversions are now performed
(incorporating the user-supplied value), the PTP timestamps will encode TAI time,
and the ptpTimescale flag is set to true.
Figure 6-11 provides a summary of the function supported by each of the manual
entries on this form:
Table 6-11. Manual Time Control Functions
Control Functionality Notes
Manual IRIG
Year Input
For IRIG inputs that do not
supply year, this entry
supplies the missing year
information. This allows
time outputs that include
the year to provide a
user-supplied correct year.
Once supplied and accepted, the year will
progress forward based on this foundation.
A quick way to check if the manually entered year
is being used is to look on the time in upper right
of web interface or front panel of S6xx.
Manual UTC
Offset from TAI
Use this control to identify
the current accumulated
leapsecond difference
between TAI and UTC
time.
TAI time is the timescale used for PTP
(1EEE-1588). Unlike UTC, TAI is not affected by
leapseconds, so to convert between these
timescales the accumulated difference due to
leapseconds must be known.
Manual Leap
Second
Notification
Use this control to identify
that a leapsecond is
pending, the direction of
the leapsecond, and the
date of its occurrence.
Once supplied and accepted (and not set to
"none") indication that a leap is pending (due
to manual entry) will appear on the
Dashboard'Timing form.
Leap pending notifications will be provided (in
the timeframe appropriate for the specific
output) for any output that is capable of
reporting pending leap.
Historically, all leapseconds have occurred at
either midnight June 30 or midnight
December 31
After the time of the leap has passed, the leap
will no longer show as pending.
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