Time-of-day synchronization with S7-1200 - STEP 7

Communications modules and network components
ft:publication_title
Communications modules and network components
Product
STEP 7
Version
V20
Publication date
11/2024
Language
en-US
Time-of-day synchronization with S7-1200

Module and synchronization method

When using an external time source, the S7-1200 station can obtain the current time of day both via the CPU as well as via a CP.

With the S7-1200 there is no forwarding of the time of day from the station to the subnet.

Time-of-day synchronization using the CPU

As the synchronization method, with the CPU only NTP can be selected.

With the "CPU synchronizes the modules of the device" option, you can cause all intelligent modules of the station (CMs, CPs) to be synchronized with the CPU time in a configurable synchronization cycle of between 10 and 86400 seconds (24 hours).

Note

Time-of-day synchronization when using Secure Open User Communication (Secure OUC)

If the S7-1200 uses Secure OUC blocks and uses the PROFINET interface of the CP for communication, the "CPU synchronizes the modules of the device" option must be enabled.

This data can only be validated against the validity period of a certificate if the date and time are current. If the date and time are outside the validity period, no communication takes place via Secure OUC.

Time-of-day synchronization using a telecontrol CP

The following synchronization methods are available:

  • NTP

    NTP can only be used when the telecontrol communication is disabled. In this case, the telecontrol CP is used as an extended PROFINET interface of the CPU.

  • Time from partner

    When telecontrol communication is enabled, the CP automatically takes the time-of-day from the communications partner.

Note

Forwarding the time to the CPU

Depending on the firmware version of the modules involved, the time-of-day of the CP is forwarded to the CPU in different ways:

  • Optional forwarding of the CP time to the CPU using a PLC tag

  • Obligatory forwarding of the CP time to the CPU via the backplane bus

Forwarding the time from the CP to the CPU

Note

Recommendation: Time-of-day synchronization only by 1 module

Only have the time of day of the station from an external time source synchronized by a single module so that a consistent time of day is maintained within the station.

When the CPU takes the time from the CP, disable time-of-day synchronization of the CPU.

The forwarding of the CP time to the CPU depends on the firmware version of the CP and the CPU. Note the following behaviour.

  • CP firmware ≤ V2.1.5

    With this firmware version the CP can make the time-of-day available to the CPU as an option via a PLC tag. When this PLC tag is read cyclically by the CPU, the CPU adopts the CP time.

  • CP firmware ≥ V2.1.7 and CPU firmware ≥ V4.2

    If both modules in a station have one of the mentioned firmware versions, the time of the CP can be forwarded automatically to the CPU.

    A condition for this is: The "CPU synchronizes the modules of the device" option is selected for the CPU under "PROFINET Interface > Time-of-day synchronization".

    Then all intelligent modules of the station are synchronized with the CPU time.

    Since the CPU automatically adopts the CP time, you no longer require the forwarding option using the PLC tag.