Rockwell Automation Publication 1756-UM542A-EN-P - September 2014 23
Chapter 4
Time Synchronization
1588 Precision Time Protocol
(CIP Sync)
The 1756HP-TIME module supports 1588 PTP which enables high-precision
time synchronization over an Ethernet network or the chassis backplane. When
PTP is selected, both Ethernet and backplane synchronization is enabled. In the
case of PTP output, the module outputs time over both the backplane and
Ethernet (if connected). In the case of PTP as a time source, the module searches
for the best clock on both media.
See the Integrated Architecture and CIP Sync Configuration Application
Te
c hn i q ue , p u b l i c at i o n
IA-AT003, for details on how to use this object.
1756HP-TIME Module as a PTP Master
When locked onto sufficient satellites, the 1756HP-TIME module can
synchronize devices to within 100 ns (by using 1588 PTP) when connected
directly to the device that is being synchronized. If these devices are connected via
a switch that does not support 1588 PTP (transparent and boundary clock
modes), the time synchronization degrades because there are more random delays
that can affect the mean-delay time calculation used for time synchronization.
Therefore, the more switches and interfaces between the 1756HP-TIME module
and the devices being synchronized, the bigger the spread of random time delays
that can result in lower time sync accuracy.
Topic Page
1588 Precision Time Protocol (CIP Sync) 23
Network Time Protocol (NTP) 26
IRIG-B 29
CST and UTC Time Conversion 30
RSLogix 5000 software, version 18.00.00 and later, or the Studio 5000
environment, version 21.00.00 and later, supports 1588 PTP.
RSLogix 5000 software, version 17.00.00 and earlier, does not support
1588 PTP.
The 1756HP-TIME module supports PTP software version 2.
Allen-Bradley Motors
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