Siemens SIMATIC S7-1200 CP 1243-8 IRC Operating Instructions Manual page 62

Configuration
4.4 Basic communication mechanisms
Communication via single or redundant telecontrol connections
The ST7 communication between two subscribers runs via configurable paths. To do this,
telecontrol connections are created in the "Network data" editor in the "Telecontrol" tab, see
section Creating telecontrol connections for the ST7 communication (Page 122).
When different networks between two subscribers have been created in the network
configuration, you can create redundant telecontrol connections. In the configuration these
are displayed in the "Network data" editor. There the main and the substitute path are
specified.
To check the reachability of a communications partner of the module, you can write the
connection status to "PLC tags for partner status / path status", see section Partner status /
path status (Page 97).
For redundant telecontrol connections, the behavior is as follows:
● Main path
If the connection between the two subscribers is undisturbed, the main path is always
used.
The status of the main path is rechecked each time there is communication and saved in
the PLC tag.
● Substitute path
If the connection via the main path is disturbed, communication is switched to the
substitute path.
The status of the substitute path, on the other hand, is only registered when
communication is established.
If you configure a dialup network connection as the substitute path via which generally a
connection is seldom established, you can test the reachability via this path for example
by synchronizing the time of day once daily via this path. To do this a connection must be
established once daily via the dialup network. The reachability is then updated once daily
in the PLC tag.
Addressing communications partners and network nodes
Since the communication between two ST7 subscribers can run via different paths and
subnets, precise addressing of the individual subscribers in the ST7 network is necessary.
The following two parameters serve this purpose:
● Subscriber number
The subscriber number is unique for every subscriber in a STEP 7 project. The following
subscribers require a subscriber number:
– TIM
– CP 1243-8 IRC, CP 1542SP-1 IRC
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Communication module for the ST7 protocol
Communication module for the ST7 protocol
Operating Instructions, 02/2018, C79000-G8976-C385-03
CP 1243-8 IRC