Siemens S7-300 appendix Assignment of S7 connections, Connection points, Transition point

Communication

3.3 S7 connections

Connection points

An S7 connection between modules with communication capability is established between connection points. The S7 connection always has two connection points: The active and passive connection points:

•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 one S7 connection of the module concerned.

Transition point

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 network transition. The module that implements this network transition is known as a router. The router is thus the point through which an S7 connection passes.

Any CPU with a DP or PN interface can be the router for an S7 connection. You can establish a certain maximum number of routing connections. This does not limit the data volume of the S7 connections.

See also

Connection resources for routing (Page 3-31)

3.3.2Assignment of S7 connections

There are several ways to allocate S7 connections on a communication-capable module:

•Reservation during configuration

•Allocating connections via programming

•Allocating connections during commissioning, testing and diagnostics routines

•Allocating connection resources to OCMS services

Reservation during configuration

One connection resource each is automatically reserved on the CPU for PG and OP communication. Whenever you need more connection resources (for example, when connecting several OPs), configure this increase in the CPU properties dialog box in STEP 7.

Connections must also be configured (using NetPro) for the use of S7 communication. For this purpose, connection resources have to be available, which are not allocated to PG/OP or other connections. The required S7 connections are then permanently allocated for S7 communication when the configuration is uploaded to the CPU.

CPU 31xC and CPU 31x, Technical data	3-27
Manual, Edition 08/2004, A5E00105475-05