Siemens Simatic S7-300 Specifications download pdf (Page 33)

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S7-300 Automation System CPU Specifications: CPU 31xC and CPU 31x

A5E00105475-03

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An S7 connection is established when S7 modules communicate with one another.

This connection represents the communication path.

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Global data communications and PtP communications do not require an S7

connection.

Every communication link requires S7 connection resources on the CPU for the

entire duration of each link.

Thus, every S7 CPU provides a specific number of S7 connection resources.

These are used by various communication services (PG/OP communication, S7

communication or S7 basic communication).

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An S7 connection between modules with communication capability is established

between connection points. The S7 connection always has two connection points:

the active and the passive connection point:

• The active connection point is assigned to the module that establishes the S7

connection.

• The passive connection point is assigned to the module that accepts the S7

connection.

Any module that is capable of communication can thus act as an S7 connection

point. At the connection point, the established communication link always uses RQH

S7 connection of the module concerned.

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If you use the routing functionality, the S7 connection between two modules

capable of communication is established across a number of subnets. These

subnets are interconnected via a gateway. The module that implements this

gateway is known as a router. The router is thus the point through which an S7

connection passes.

Any CPU with a DP interface can be the router for an S7 connection. They can

establish up to four routed connections (or up to 8 with CPU 317-2 DP) without

restricting the equipment required for the S7 connections.

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Siemens Simatic S7-300 Specifications Page 33