Siemens Simatic RTU303xC Series Operating Instructions Manual page 167

The time-of-day synchronization is performed with the communication cycle.
● Always remain connected
If you enable this option, the RTU remains permanently in the communication mode and
connected to the communications partner.
● Basic cycle
From the drop-down list, specify the basic cycle (3 minutes ... 7 days) for communication.
● Start time of the communication cycle
Synchronizes the communication cycle with this time of day.
The communication mode starts with a lead time so that the RTU is reachable at the
configured times. The lead time of the RTU is made up of the following times:
– 15 seconds (basic lead time for the configured mobile wireless interface)
– + 10 seconds with activated DHCP client
– + 45 seconds with data service configured
– + 15 seconds with OpenVPN service configured
When using the LAN interface in communication mode via an external router, the lead
time configured there applies, see section LAN (Page 130).
If shortly before expiry of the minimum duration the connection still needs to remain
established (e.g. sending an e-mail), the communication mode is extended by the
required time.
● Start day of the communication cycle
Synchronizes the communication cycle with this day.
The option is only available if "7 days" is configured as the basic cycle.
● Minimum duration
After connection establishment, the RTU first sends its stored data (messages, event-
related process data) to the partner. Under certain circumstances in mobile wireless
networks it can take a while for a response from the partner to reach the RTU.
So that the RTU does not terminate the connection too early without having received new
data from the partner or without the OpenVPN connection being established, you can
configure a waiting time here (30 s ... 10 min).
The RTU maintains the connection for the configured Minimum duration as of the
configured start time.
If you select "No" the RTU terminates the connection after sending its own data and
receiving the acknowledgement from the partner, however at the earliest at the
configured start time.
● Start test communication mode
By clicking the button you can turn on the communication mode for test purposes, for
example during commissioning.
RTU303xC
Operating Instructions, 06/2019, C79000-G8976-C382-06
Configuration (WBM)
4.18 Operating mode
167