Hirschmann MACH 4000 Series, Руководство пользователя

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Synchronizing the System Time of the
Basic - L3P
Release 3.1 06/07
7.3 Precison Time Protocol
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The cable delays are relatively constant. Changes occur very slowly. This
fact is taken into account by IEEE 1588 by performing measurements and
calculations on a regular basis.
IEEE ignores the inaccuracy caused by device delays and device jitter
through the definition of “boundary clocks”. Boundary clocks are clocks that
are integrated into the devices. These clocks are synchronized on the one
side of the signal path and, on the other side of the signal path, are used to
synchronize the subsequent clocks (ordinary clocks).
Fig. 29: Boundary Clock
Independent of the physical communication paths, the PTP provides logical
communication paths that you define when you set up PTP subdomains.
Subdomains are designed to create groups of clocks that are time-indepen-
dent of the rest of the domain. Typically, the clocks use the same communi-
cation paths that other clocks do.
GPS
Reference
(Grandmaster Clock)
Master Slave
Boundary Clock
Ordinary Clock
Ordinary Clock
Switch
PLC