Configuring Time Synchronization

Introduction

The synchronizes the clock in the 140NOC78000 distributed I/O head module to that of the time server. The synchronized value is used to update the clock in the PLC. Typical time service configurations utilize redundant servers and diverse network paths to achieve high accuracy and reliability.

Use the time service for:

event recording (sequence events)
event synchronization (trigger simultaneous events)
alarm and I/O synchronization (time stamp alarms)

Time Synchronization Service Features

Some features of the time synchronization service are:

periodic time correction obtained from the reference-standard time server
automatic switch over to a backup time server if a detected problem occurs with the normal time server system
controller projects use a function block to read the accurate clock, a feature that allows project events or variables to be time stamped
estimated time stamping accuracy of:
- 5 msec for 140 CPU 651 •0s and later
- 10 msec for other CPUs
local time zone is configurable, including daylight savings time

Time Synchronization Process

The 140NOC78•00 control head module contains an SNTP client, which provides time synchronization.

Action	Result
An SNTP client requests a time synchronization signal from an SNTP server. (The request is sent over an Ethernet network.)	The SNTP server responds with a signal.
The SNTP client stores the time.
The SNTP client sends a message to the controller’s clock system counter.	The controller updates its internal clock.
Use the R_NTPC function block in either MAST, FAST, or Interrupt sections to read the clock from the PLC application.

On an Ethernet network, all controllers should be synchronized with the same SNTP server.

Power Up

To establish the accurate Ethernet system network time, the system performs the following at power up:

requires the 140NOC78000 head module to boot
uses the 140NOC78000 head module to obtain the time from the SNTP server
requires a predefined interval until time is accurate; your configuration determines how long before time is accurate
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 140NOC78100 head module.

Model	Starting Date
Modicon Quantum with Control Expert	January 1st 1980 00:00:00.00

Stop or Run PLC

Stop and run have no effect on the accuracy of the clock.
Stop and run have no effect on the update of the clock.
A transition from one mode to the other has no effect on the accuracy of the Ethernet system 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 SNTP server swap.

There will be 2 polling periods before the time is accurate.

Configuring the Time Synchronization Service

To configure the time synchronization service:

Step	Action
1	Open the 140NOC78000 head module in the DTM browser.
2	In the Services page, set the Network Time Service field to Enabled.
3	Click the Network Time Service node in the Services navigation tree in the left panel.
4	Enter changes in the appropriate fields on the Network Time Service configuration page. The table below describes the configuration page parameters.
5	Click Apply to save changes, or click OK to save changes and close the window.

Time Synchronization Configuration Parameters

Field	Parameter	Action
NTP Server Configuration
	Primary NTP Server IP Address	Enter a valid IP address.
	Secondary NTP Server IP Address	Enter a valid IP address.
	Polling Period	The polling period is the time (in seconds) between updates from the SNTP server. To obtain optimal accuracy (and if your network allows), reduce the polling period to a small value. The default is 5 seconds. Enter a value: min = 1 sec max = 120 sec
Time Zone
	Time Zone	Select the desired time zone from the drop-down list. The default value is your current system’s time zone (as found in Windows). You can also select Custom Time Zone.
	Time Zone Offset	If you selected Custom Time Zone, enter a value in the range of (24 hours * 60 minutes - 1) [1-minute step].
Daylight Saving
	Automatically adjust clock for daylight saving change	Disabled: In the Start Daylight Saving and End Daylight Saving fields, enter the month, day of week, and occurrence range from the respective drop-down lists. Disabled is the default. Enabled: The 140 NOC 78• 00 head module automatically corrects the local time to account for daylight saving time. The Start Daylight Saving and End Daylight Saving fields are disabled because their times are automatically changed in the spring and fall every year.
	Start Daylight Saving	Month: January to December Day of Week: Sunday to Saturday Occurrence: 1 to 5
	End Daylight Saving	Month: January to December Day of Week: Sunday to Saturday Occurrence: 1 to 5
CPU Time Update
	Update CPU time with this module	Select True or False from the drop-down list. False is the default.