CM 100 High
User Manual
42
4.6
Synchronisation of several devices by PTP (802.1AS)
802.1AS is a protocol used between two or more devices to synchronize all of them
through an Ethernet communication. This synchronization allows two or more devices
(one master and one or multiple slaves) to transmit/receive time-critical information
through a physical link and assures that all the devices will handle the same time
reference. By the example of the CaptureModules it is the timestamping of logged
data. The CaptureModules allow a synchronization between each other and other
devices by 802.1AS PTP.
4.6.1
Transport of time-synchronization information
For the reference case where this communication is established only between two
devices,
„Time
-aware system i-
1“ configured as 802.1as master and „Time
-aware
system i+1“ configur
ed as slave, the ports of the CaptureModule
(„Time
-aware system
I”) implements additionally then the respective opposite sides of
the communication,
one slave port and one master port, as shown in the next image.
Figure 4-22: 802.1AS PTP bridge
The time-synchronization information contained on the Sync and Follow Up messages
sent by the „Time
-aware system i-
1“
is redirected and received CaptureModule.
These packets are decoded, and the relevant information extracted. The extracted
information is used later to generate, together with the information extracted from the
propagation delay algorithm, the new corrected Sync and Follow Up messages that will
