26 Rockwell Automation Publication 1756-UM542A-EN-P - September 2014
Chapter 4 Time Synchronization
PTP as a Time Source
The 1756HP-TIME module can be set to be a PTP slave. The module
synchronizes to the best PTP clock on either the backplane or the Ethernet
network, using the best master clock algorithm (BMC).
Using PTP as the time source enables NTP and IRIG-B as the output modes.
T
herefore, the accuracy is limited to the accuracy of the respective output modes.
Network Time Protocol (NTP)
This section describes how to configure the 1756HP-TIME module as an NTP
server or an NTP client.
1756HP-TIME Module as an NTP Server
The 1756HP-TIME module supports NTP, which provides time
synchronization over an Ethernet network. NTP clients can be synchronized to
approximately 1ms of the NTP client, depending on the network configuration
and reliability.
NTP is typically used when synchronizing personal computers or domain
con
trollers. You can use the Hiprom Software Network Time Protocol
(HSNTP) application to set the Windows time service on a personal computer
to synchronize to the 1756HP-TIME module. Download the HSNTP
application from
www.hiprom.com.
The TIME module cannot act as a boundary clock. If PTP is selected as the input
time source, then PTP output is disabled.
The accuracy of the PTP time is dependent on the quality and reliability of the
Ethernet network. The PTP algorithm allows for network delays, but needs a
constant delay to synchronize accurately. PTP switches prioritize PTP messages
to keep the delay constant, and are preferred for PTP networks.
The 1756HP-TIME module supports NTP version 3, RFC1305.
When a computer is on a domain, it tries to synchronize to the domain
controller. Therefore, you can set up the domain controller to synchronize to
the 1756HP-TIME module.
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