You can configure an M580 CPU as an NTP server or an NTP client in the Control Expert NTP tab.

When the CPU firmware version is:

  • Earlier than V4.01, the SNTP protocol is employed and you can configure the CPU as:

    • NTP client

    • NTP server

    • Both NTP client and server

  • V4.01 or later, the NTPv4 protocol is employed and you can configure the CPU as:

    • NTP server only

    • NTP server and client

To begin, open the CPU configuration tabs in Control Expert.

NTP Service Features

The NTP service has these features:

  • A periodic time correction is obtained from the reference-standard time server.

  • There is an automatic switchover to a backup (secondary) time server if an error is detected with the normal time server system.

  • Controller projects use a function block to read the accurate clock, allowing project events or variables to be time stamped. (Refer to the System Time Stamping User Guide for detailed information about timestamping performance.)

NOTE:

When the M580 CPU is configured as either an NTP server or as an NTP client, the BM•CRA312•0 (e)X80 EIO adapter modules are NTP clients of the CPU:

  • When only BM•CRA31200 modules are configured as NTP clients, the accuracy of this server allows time discrimination of 20 ms.

  • All BM•CRA31200 modules in the network have the same client configuration.

NTP Client Mode

When the CPU is configured as an NTP client, the network time service (SNTP or NTPv4) synchronizes the clock in the M580 CPU to that of the time server. The synchronized value is used to update the clock in the CPU. Typical time service configurations utilize redundant servers and diverse network paths to achieve high accuracy and reliability.

When the CPU firmware version is:

  • Earlier than V4.01, you can specify a primary and secondary NTP server.

  • V4.01 and later, you can identify up to 8 NTP servers, and specify the preferred server.

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

  • requires the CPU to boot

  • uses the CPU to obtain the time from the NTP 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 CPU.

Model

Starting Date

Modicon M580 with Control Expert

January 1st 1980 00:00:00.00

Stop or run CPU:

  • 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 M580 CPU is reinitialized after an application is downloaded or after an NTP server swap. The time is accurate after two polling periods.

NOTE: For NTP diagnostics, refer to the NTP web page.

NTP Server Mode

When the CPU is configured as an NTP server, it can synchronize client clocks (such as a BM•CRA31200 (e)X80 EIO adapter module). The CPU's internal clock is then used as reference clock for NTP services.

NTP Parameters for a CPU with Firmware earlier than V4.01

Use the pull-down menu in the NTP field to configure the CPU as an NTP Client or an NTP Server:

Value

Comment

Disabled

default: Both the NTP server and the NTP client services of the CPU are disabled.

NTP Client

The CPU functions as the NTP client. In this case, configure the NTP Server Configuration parameters.

NOTE: Enable the NTP client here to automatically enable the NTP client service on all BM•CRA312•0 adapter modules.

NTP Server

The Ethernet I/O scanner CPU acts as an NTP server.

NOTE: Enable the NTP client here to automatically enable the NTP client service on all BM•CRA312•0 adapter modules and to configure the BM•CRA312•0 to use the CPU as the NTP server.

Assign values to these parameters in the NTP Server Configuration field:

Parameter

Comment

Primary NTP Server IP address

the IP address of the NTP server, from which the CPU first requests a time value

Secondary NTP Server IP address

the IP address of the backup NTP server, from which the CPU requests a time value after not receiving a response from the primary NTP server

Polling Period

The time (in seconds) between updates from the NTP server. Smaller values typically result in better accuracy.

NOTE: This parameter applies only to the SNTP protocol and to CPUs using a firmware version earlier than V4.01.

NTP Parameters for a CPU with Firmware V4.01 or later

Use the following settings to configure the NTP protocol:

Parameter

Description

Server Only / Client Server

Specify the NTP role of the CPU: server only, or both client and server.

Stratum

The relative position of the server in the NTP network. This represents the distance of the CPU (in its role as NTP server) from the reference clock.

  • 0 is lowest (directly connected)

  • 15 is most distant (hence less reliable)

When the CPU is operating as:

  • Client and server: this parameter is auto-configured. It is equal to the stratum value of the system peer +1.

  • Server only or in orphan mode (i.e., when the CPU’s subnet becomes isolated from other NTP servers and assumes the role as interim server): you can configure this parameter.

Server IPv4 address1

The IP addresses of reference NTP servers used by the CPU. Minimum of 4; maximum of 8.

Used as preferred1

Indicates the NTP server in the list to be used by the CPU.

Quality threshold (ms)1

Threshold for NTP accuracy. Setting range 0...1000.

  • 0 = not used.

  • Default value = 50 ms.

The Quality threshold setting is compared to the DDT value NTP_WITHIN. If the Quality threshold is ≥ NTP_WITHIN, the NTP_QUALITY_WARNING DDT item is set to true (1) and the event is recorded in syslog.

1. If Server Only is selected, these parameters are disabled.