Baumer VLXT - Category: Transportlayercontrol → Ptpcontrol (≥ Release 2 Only)

198
V2.6 | 8/30/2022 | 1120758
7.20.4 Category:TransportLayerControl→PtpControl(≥Release2only)
Category that contains the features related to the Precision Time Protocol (PTP) of the
device.
General Information
IEEE 1588 Precision Time Protocol (PTP) manages clock synchronization of multiple
devices across an Ethernet network. On a local area network, it achieves clock accuracy
in the sub-microsecond range, making it suitable for measurement and control systems.
PTP was designed to improve on existing clocksynchronization methods such as Network
Time Protocol (NTP) and Global Positioning System (GPS). NTP suffers from poor accu-
racy, often quoted to be several milliseconds using a fast Ethernet network. GPS provides
nanosecond precision using atomic clock and satellite triangulation; however, it is an ex-
pensive component to incorporate into a camera.
PTP provides microsecond precision without increasing component cost, providing better
accuracy than NTP at a lower cost than GPS.
The diagram below shows the steps taken to synchronize the slave clock to that of the
master.
Master clock
appearing synchronized
Sync (t
1 estim
)
Follow_up (t
1
)
Delay_Req
Delay
Offset
Offset
Delay_Resp(t
4
)
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
t
1 estim
t
1
-
t
4
-
200
300
400
500
600
700
800 - t
2
900
1000 - t
3
1100
1200
1300
1400
1500
1600
1700
Slave clock
Delay
PTP synchronization
Synchronization begins when the device congured as the Master PTP clock transmits
a Sync telegram using multicast messaging. Devices congured as Slave PTP clocks
calculate the time difference between their clock and the Master PTP clock, and adjust
accordingly.
Slave clock frequencies are constantly adjusted, through follow up and delay messages,
to keep their clock value as close as possible to the master clock. While all Slave clocks
are within 1 μs of the master, PTP sync is achieved.
Notice
Release≥3only
The feature PtpSer-
voStatusThreshold
can be used to set the
time threshold when
the transition from
PtpServoStatus =
Unknown to PtpSer-
voStatus = Locked
is done and back.