Network Time Service Configuration in the DTM

Introduction

The BMENOR2200H module supports clock synchronization as an client.

When the SNTP client is enabled, the module synchronizes the internal clock from the time server. This time is the basis for time stamping RTU events.

NOTE: For details, refer to the description of the BMENOR2200H module as an SNTP client.

Features of the Service

The clock synchronization via SNTP offers:

periodic time corrections obtained from the reference standard, for example, the SNTP server
automatic switchover to a backup time server if an abnormal event is detected with the normal server system
local time zone configurable and customizable (including daylight saving time adjustments)

Controller projects use a function block to read the clock, a feature that allows events or variables in the project to be time stamped.

Time stamping is accurate to:

5 ms typical
10 ms worst case

Access the SNTP Configuration

Access the SNTP parameters in the Control Expert :

Step	Action
1	Access the DTM configuration for your module.
2	In the CONFIGURATION menu, expand (+) the Communication sub-menu.
3	Select Network Timing Service.
4	Configure the SNTP parameters. NOTE: The parameters are described in the next table.
5	Click the Apply button to implement your configuration changes. Click the OK button to implement your changes and close the dialog box.

Time Synchronization Parameters

This table shows the SNTP parameters that are available for your module:

Field	Parameter	Description
SNTP Server	Primary IP Address	Enter a valid IP address for the primary SNTP server.
	Secondary IP Address	Enter a valid IP address for the secondary SNTP server.
	Polling period	This value represents the number of seconds between updates from the SNTP server.
Time Zone	Time Zone	Select a time zone from the pull-down menu.
	Timezone Offset	This value represents the difference (in minutes between the configured time zone and UTC.
	Automatically adjust clock for daylight saving	selected: Adjust the clock for daylight saving time.
	Automatically adjust clock for daylight saving	deselected: Do not adjust the clock for daylight saving time.
	Start Daylight Saving	Configure the start and end times for daylight saving in the available fields.
	End Daylight Saving
TIME TO CPU	Update Clock to CPU	selected: Update the clock with the time from the CPU.
TIME TO CPU	Update Clock to CPU	deselected: Do not update the clock with the time from the CPU.

NOTE: When the Control Expert window is active, you can hover the cursor over any parameter field to see a description of the functionality and the available range of values.

Clock Synchronization Terms

SNTP terms:

Term	Description of Service
local clock offset	Accurate local time adjustments are made via a local clock offset. The local clock offset is calculated as: ((T2 - T1) + (T4 - T3))/2 where: T1 = time when SNTP request is transmitted from the module T2 = time when SNTP server receives the request (provided by the module in response) T3 = time when the SNTP server transmits the response (provided to the module in the response) T4 = time when SNTP response is received by the module
time accuracy	The local time margin is < 10 ms compared to the referenced SNTP server time. typical: 5 ms worst case: <10 ms
settling time	Maximum accuracy is obtained after 2 updates from the SNTP server.
polling period dependency	Accuracy depends on the polling period. Less than 10 ms of margin is achieved for polling periods of 120 ms or less. To obtain a high degree of accuracy (when your network bandwidth allows), reduce the polling period to a small value—for example, a polling time of 5 s provides better accuracy than a time of 30 s.
leap second	To compensate for the deceleration of the earth rotation, the module automatically inserts a leap second in the UTC time every 18 months via an international earth rotation service (IERS). Leap seconds are inserted automatically as needed. When needed, they are inserted at the end of the last minute in June or December, as commanded by the SNTP server.

Obtaining and Maintaining Accuracy

The time service clock starts at 0 and increments until the Ethernet network time is fully updated from the module.

Model	Starting Date
M580	January 1, 1980 00:00:00.00

Clock characteristics:

Clock accuracy is not affected by issuing stop/run commands on the PLC.
Clock updates are not affected by issuing stop/run commands on the PLC.
Mode transitions do not affect the accuracy of the Ethernet network.

NOTE: For details, refer to the descriptions of available time sources.

General Time Synchronization Terms

General terms:

Term	Description of Service
time zone	The default format is universal time, coordinated (UTC). Optionally you may configure the service to use a local time zone (for example, GMT+1 for Barcelona or Paris). Refer to the note at the end of this table.
daylight saving time	The module automatically adjusts the time change in the spring and fall. Refer to the note at the end of this table.
update clock to CPU	When no other time source is configured, the RTU receives a UTC time for synchronization from the CPU over the Ethernet backplane.
NOTE: This setting is implemented at the module level even if there is no SNTP configuration for the module. The implementation of this setting owes to the BMENOR2200H module's support for several time sources (for example, DNP3). It you, therefore, use DNP3 for time synchronization instead of SNTP, the time zone is applied to the module.