Spectracom NetClock 9400 Series, Руководство пользователя

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GNSS Receiver (if available as an input reference): The GNSS satellite system transmits
information regarding a Leap Second adjustment at a specific Time and Date an arbit
rary number of months in advance.
Input references other than GNSS : Some of the other available input references (e.g.,
IRIG, ASCII, NTP) can also contain pending Leap Second notification in their data
streams (see chapter below).
Manual user input : NetClock can be manually configured with the date/time of the next
pending Leap Second. On this date/time, the System Time will automatically correct for
the Leap Second (unless the System Time’s timescale is configured as either GPS or TAI).
3.2.3.2 Leap Second Alert Notification
NetClock will announce a pending Leap Second adjustment by the following methods:
ASCII Data Formats 2 and 7 (among other formats) from the ASCII Data option modules
contain a Leap Second indicator. During the entire calendar month preceding a Leap
Second adjustment, these Formats indicate that at the end of the current month a Leap
Second Adjustment will be made by using the character ‘L’ rather than a ‘_ ‘ [space] in
the data stream. Note that this does not indicate the direction of the adjustment as
adding or removing seconds. These formats always assume that the Leap Second will be
added, not removed.
NTP Packets contain two Leap Indicator Bits. In the 24 hours preceding a Leap Second
Adjustment, the Leap Indicator Bits (2 bits) which normally are 00b for sync are 01b (1)
for Add a Leap Second and 10b (2) for Remove a Leap Second. The bit pattern 11b (3)
indicates out of sync and in this condition NTP does NOT indicate Leap Seconds. The
Sync state indicates Leap Seconds by indicating sync can be 00b, 01b, or 10b.
PTP Packets provide leap indication with a 12-hour notification window.
Some IRIG formats provide leap second notification indicators.
Note: It is the responsibility of the client software utilizing either the Data Formats
or NTP time stamps to correct for a Leap Second occurrence. NetClock will make
the correction at the right time. However, because computers and other systems
may not utilize the time every second, the Leap Second correction may be
delayed until the next scheduled interval, unless the software properly handles the
advance notice of a pending Leap Second and applies the correction at the right
time.
3.2.3.3 Leap Second Correction Sequence
The following is the time sequence pattern in seconds that NetClock will output at UTC midnight
on the scheduled day (Note: This is NOT local time midnight; the local time at which the adjust
ment is made will depend on which Time Zone you are located in).
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NetClock User Reference Guide Rev. 16
3.2 System Time