Rockwell ArmorStratix 5700 series, Инструкция по эксплуатации

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194 Rockwell Automation Publication 1783-UM007F-EN-P - September 2016
Chapter 7 Configure Switch Features
CIP Sync Time
Synchronization
(Precision Time Protocol) CIP Sync time synchronization refers to the IEEE 1588 standard for Precision
Time Protocol (PTP). The protocol enables precise synchronization of clocks
in measurement and control systems. Clocks are synchronized with
nanosecond accuracy over the EtherNet/IP communication network. PTP
enables systems that include clocks of various precisions, resolution, and
stability to synchronize. PTP generates a master-slave relationship among the
clocks in the system. All clocks ultimately derive their time from a clock that is
selected as the grandmaster clock.
By default, PTP is disabled on all Fast Ethernet and Gigabit Ethernet ports.
You can enable or disable PTP on a per-port basis. For a list of switches that
support PTP, see
page 21 .
To configure PTP, you choose one of these clock modes:
• Boundary mode
• End to End Transparent mode
• Forward mode (default)
• NTP-PTP Clock mode
For more information about these modes, refer to the Converged Plantwide
Ethernet Design and Implementation Guide, publication
ENET-TD001 .
Boundary Mode
In Boundary mode, the switch participates in selecting the best master clock. If
the switch does not detect a better clock, the switch becomes the grandmaster
clock on the network and the parent clock to all connected devices. If the best
master is determined to be a clock connected to the switch, the switch
synchronizes to that clock as a child to the clock, and then acts as a parent clock
to devices connected to other ports.
After initial synchronization, the switch and the connected devices exchange
timing messages to correct time skew caused by clock offsets and network
delays. This mode can eliminate the effects of latency fluctuations. Because
jitter and errors can accumulate in cascaded topologies, choose this mode only
for networks with fewer than four layers of cascaded devices.
The clock selection process is determined in part by the relative priority of the
switches in the network. You can define the priorities of switches in the
Priority 1 and Priority 2 fields in either Device Manager or the Logix Designer
application.
In Boundary mode, one or more switch ports can be PTP-enabled.