S7 Connections - Siemens SIMATIC ET 200S Manual

8.7

S7 connections

Introduction
If S7 modules communicate with each other, a so-called S7 connection is built up
between the modules. This forms the communication route.
Note
Global data communication does not require S7 connections.
Each communication connection requires S7 connection resources on the CPU;
these must exist for the duration of the specific connection.
Therefore, a specific number of S7 connection resources is made available on
each S7 CPU that are used by different communication utilities (PD/OP
communication, S7 communication or S7 basic communication).
What are S7 connection points?
The S7 connection between communications-capable modules is established
between connection points. Therefore, the S7 connection always has two
connection points: an active and a passive connection point.
S The active connection point is assigned to the module that builds up the S7
connection.
S The passive connection point is assigned to the module that accepts the S7
connection.
Each communications-capable module can become a connection point of an S7
connection. At the connection point, the established communication connection
always occupies one S7 connection of the specific module.
Pass-through point of an S7 connection
If you use the routing functionality, the S7 connection between two
communications-capable modules is built up over several subnetworks. These
subnetworks are connected to each other through a gateway. The module that is
used to implement this gateway is called the router. Thus, the router is the
pass-through point of an S7 connection.
The IM 151-7 CPU can be a router of an S7 connection if a DP master module has
been plugged in. The IM 151-7 CPU can build up a maximum of 4 routing
connections that do not restrict the quantity structure of the S7 connections.
ET 200S IM 151-7 CPU Interface Module
A5E00058783-04
Functions of the IM 151-7 CPU
8-29