Time-of-day synchronization in SIMATIC mode:
In "SIMATIC" mode, the CP forwards MMS time-of-day messages when it receives them from a SIMATIC time transmitter. The time-of-day messages can either be received via the backplane bus or via the communications bus (S7-400 CPU) or via LAN.
"Apply time in CP"
The time of day can either be simply received by the CP or received and forwarded.
When the time-of-day is forwarded, you need to specify the direction in which it is forwarded.
"Direction"
Depending on where the time master is located, the direction of the time-of-day forwarding must be taken into account.:
If you have several CPs in your station, take into account the flow of time-of-day messages depending on the time-of-day master since you can forward time-of-day messages from one network to another network using the function described here. In a station there must only be one time master.
If there are several CPs that are connected to the same subnet and if forwarding of the time of day is activated for these, the following applies: The CP with the lowest slot number handles the forwarding of the messages. All other CPs configured for forwarding time-of-day messages, automatically stop forwarding.
You can make the following settings for the direction of time-of-day forwarding:
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Automatic
The CP receives the timeofday message from the LAN or from the station and forwards it to the station or to the LAN.
If several CPs are being operated in the station, this automatic setting can lead to collisions. To avoid this, you can specify the direction of forwarding with the following options:
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From station
The CP receives the time-of-day message from the station and forwards it to the LAN.
In this case, a local CPU must be configured as the time master or another CP 400 forwards time messages to the K bus.
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From LAN
The CP receives the time-of-day message from LAN and forwards it to the station.
In this case, the local CPU must be configured as a time slave.
Exception: CPU 318
"Use corrected time"
With the this option, you can decide whether a correction factor in the time-of-day frame is taken into account.
The correction factor that can be set in a central clock SICLOCK in units of ½ hours specifies a time offset for example to correct a time zone setting or standard/daylight saving time.
If this option is enabled, the CP calculates the correction factor in the time of day to be forwarded this so that systems to which the time is forwarded do not need to take the factor into account.
Example:
The time 9:21 is transferred in the time-of-day frame. In addition, the time-of-day frame contains the correction factor +2 x 0,5 (= 1h). The time forwarded by the CP is therefore 10:21.