Entry type: FAQ, Entry ID: 37112, Entry date: 07/07/2006

How many connection resources can be managed by the C7-CPU or the C7-OP?

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Every communication connection needs connection resources on the respective device:

  • for the PG-communication
  • for the OP-communication
  • for the S7-basis communication

1. C7-CPU
In principle several connections can be managed by the C7 CPU. These are split up as follows:

  • A connection is reserved for the PG. It can't be used for other purposes. Consequently it is guaranteed at any time, that a (service-) PG can be connected in case of an error.
  • A second connection is reserved for the C7-OP. 
  • Furthermore "spare" connections are available for user-defined use (view table 1).

The communication modes "Global data" (GD) and "Decentralized periphery" (DP) do not use the connection resources.

2. C7-OP
A C7-OP can manage several connection resources. These are split up as follows:

  • A connection of the C7-OP is reserved for the ("internal") C7 CPU (exception C7 613).
  • Further connections are at the users disposal, which can be assigned to user-defined "external" controllers. This might be further C7, S7 300 or S7 400 controllers.

Assign the connection resources in the configuration environment of ProTool or ProTool/Lite.

C7 device

Number of CPU connections

Number of OP connections


C7-635 12 4
C7-636 16 6
Table 1: Maximum possible communication connections on a C7 device 

A CP 342-5 can be used in order to increase the number communication stations (connections) in the C7-CPU.

More information on this topic area is available in

  • the manual on "Communication with SIMATIC" in Entry ID 1254686.
  • the manual on "SIMATIC Complete Device C7-613" in Entry ID 13125532.
  • the manual on "SIMATIC Complete Device C7-635" in Entry ID 11559312.
  • the manual on "SIMATIC Complete Device C7-636" in Entry ID 18230904

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