Setting Up A Connection - Siemens SIMATIC ET 200AL System Manual

Available connection resources in a station
The maximum number of resources of a station is determined by the CPU.
Each CPU has reserved connection resources for PG, HMI and web server communication. In
addition, there are available resources for other communication services, e.g. for SNMP, e-
mail connections, HMI and S7 communication as well as for open communication.
When are connection resources allocated?
The time for allocation of connection resources depends on how the connection is set up,
automatic, programmed or configured (see section Setting up a connection (Page 33)).
Additional information
You will find more detailed information on the allocation of connection resources and the
display of connection resources in STEP 7 in the section Connection resources (Page 391).
3.4

Setting up a connection

Automatic connection
STEP 7 sets up a connection automatically (for example PG or HMI connection) if you have
connected the PG/PC interface to an interface of the CPU physically and have made the
interface assignment in STEP 7 in the "Go online" dialog.
Setting up a programmed connection
You set up the programmed connection in the program editor of STEP 7 in the context of a
CPU by assigning instructions for communication, for example TSEND_C.
When specifying the connection parameters (in the Inspector window, in the properties of
the instruction), you are supported by the easy-to-use user interface.
Communication
Function Manual, 05/2021, A5E03735815-AJ
Communications services
3.4 Setting up a connection
33