User manual

Using the NTPTime Service
33002479 06 07/2008 249
NTP Time Synchronization Service Operating Conditions
Introduction This material describes special operating conditions related to:
z powering up
z stop or run PLC
z downloading applications
z configuring the time service
Power up To establish the accurate Ethernet system network time, the system does the
following at power-up:
z requires the Ethernet module to boot
z uses the Ethernet module to obtain the time from the NTP server
z requires a predefined interval until time is accurate; user’s configuration
determines how long before time is accurate
z may require several updates to achieve peak accuracy
Once an accurate time is received, the service sets the STATUS in the associated
time service register.
The time-service clock value starts at 0 until fully updated from the module.
Stop or Run PLC z Stop and Run have no effect on the accuracy of the clock.
z Stop and Run have no effect on the update of the clock.
z A transition from one mode to the other has no effect on the accuracy of the
system Ethernet network time.
Download
Application
The status clock value associated with the time service register in the CPU is
reinitialized after an application is downloaded or after an NTP server swap.
There will be two polling periods before the time is accurate.
NTP
Configuration
The time service topic (see Configuring the Time Synchronization Service, p. 290)
contains information about NTP configuration.
Model Starting Date
Modicon Quantum with Unity January 1st 1980 00:00:00.00