When the Time reference is configured as
Local System
, VelaSync's System
Time is considered a valid reference, as long as the external 1PPS input reference
is valid.
Vice versa, when the 1PPS reference is configured as
Local System
, VelaSync's
built-in oscillator is considered a valid reference, as long as the external Time ref-
erence is valid.
Use case "Local System Time"
The
Local System
reference when used for
Time
allows VelaSync to operate using its
current Time-of-Day (ToD) for Time, while synchronized to an external 1PPS reference.
While you may intentionally offset the time in this scenario, the second will be precisely
aligned to the external 1PPS reference. Therefore, this use case qualifies as a legitimate,
traceable time source.
Instead of an offset time,
Local System
can also be used as a backup Time reference
(e.g., Priority "2"): Should the external Time reference become invalid, the
Local Sys-
tem
Time will become the valid backup reference, disciplined by the external 1PPS ref-
erence: VelaSync will transition to the
Local System
Time, without going into Holdover.
Use case "Local System 1PPS"
The
Local System
reference can also be used for
1PPS
: This allows VelaSync to operate
using an external ToD for time, while generating 1PPS from its own internal oscillator.
In this rare use case the 1PPS is NOT aligned to any standard, therefore the time may
drift, and must be considered untraceable.
3.3.1.3 The "User/User" Reference
While it is normally not required, it is possible for you as the "User" to override the
Sys-
tem Time
(even if it is synchronized to a valid reference) with a manually set time,
steered by an undisciplined oscillator, and use this manually set Time as an output ref-
erence. This concept is referred to as the
User/User
reference, because both the Time,
and the 1PPS reference are not linked to any UTC-based external reference, but hand-
set by you.
Caution:
Since the
User/User
reference is not traceable to a valid ref-
erence, it does not qualify as a legitimate time source. Operating
VelaSync with a manually set
User
time bears the risk of inadvertently
outputting an illegitimate System Time thought to be a valid reference
time.
116
CHAPTER
3
•
VelaSync User's Manual Rev. 3
3.3 Managing References
Summary of Contents for VelaSync 1225
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