User manual

Ethernet Communication Services
90
33002479 06 07/2008
Time Synchronization Service
General The time service synchronizes computer clocks over the Internet. For example, the
time of one client is synchronized either with another server or to a referenced time
source like a radio or satellite receiver.
Typical time service configurations utilize multiple redundant servers and diverse
network paths to achieve high accuracy and reliability. Time service accuracy can
be within a millisecond on LANs and up to a few tenths of milliseconds on WANs.
Use the time service for:
z event recording: sequence events
z event synchronization: trigger simultaneous events
z alarm and I/O synchronization: time stamp alarms
Time Synchroni-
zation and Time
Stamps
On an Ethernet network, all controllers should be synchronized with the same clock
time, which is provided by an NTP server. In each application program, events or
application data (I/O values for example) can be time stamped using the application
stacks.
The Modicon Quantum Ethernet interface module, an NOE 771 11, connects to an
NTP time server and provides the source-time synchronization signal, which is sent
to the CPU.
To read the clock, a function block is used in the controller’s project (application
program):
CPS CPU NOE
Clock
System
Counter
NTP
Client
NTP Request
NTP Response
Ethernet
Network
NTP
Server
Premium System
EN
R_NTPC
EN0
OUT1
OUT2
STATUS