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
VelaSync 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 pre-
ceding 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 occur-
rence. VelaSync 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 VelaSync will output at UTC
midnight on the scheduled day (Note: This is NOT local time midnight; the local time at
which the adjustment is made will depend on which Time Zone you are located in).
A.
Sequence of seconds output when
adding a second
("positive Leap Second"):
56, 57, 58, 59,
60
, 0, 1, 2, 3 …
3.2 System Time
CHAPTER
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VelaSync User's Manual Rev. 3
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Summary of Contents for VelaSync 1225
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Page 34: ...BLANK PAGE 1 9 Regulatory Compliance 22 CHAPTER 1 VelaSync User s Manual Rev 3...
Page 104: ...BLANK PAGE 2 11 Configuring PTP 92 CHAPTER 2 VelaSync User s Manual Rev 3...
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