Assignment Of S7 Connections - Siemens SIMATIC S7-400 Manual

4.3.2

Assignment of S7 connections

There are several ways to allocate S7 connections on a communication-capable module:
● Reservation during configuration
● Assigning connections in the program
● 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, increase the number 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.
Assigning connections in the program
In basic S7 communication and in open Industrial Ethernet communication with TCP/IP, the
user program establishes the connections. The CPU operating system initiates the
connection. S7 basic communication uses the corresponding S7 connections. The open
IE communication does not use any S7 connections.
Using connections for commissioning, testing and diagnostics
An active online function on the engineering station (PG/PC with STEP 7) occupies
S7 connections for PG communication:
● If an S7 connection resource for PG communication is reserved in your CPU hardware
● If all reserved S7 connection resources for PG communication are allocated, the
Allocating connection resources to OCMS services
S7 connection resources are allocated for the OP communication by an online function on
the HMI station (OP/TP/... with
● If an S7 connection resource for OP communication is reserved in your CPU hardware
● If all reserved S7 connection resources for OP communication are allocated, the
S7-400 Automation System, CPU Specifications
Manual, 10/2006, 6ES7498-8AA04-8BA0
configuration, it is assigned to the engineering station, that is, it only needs to be
allocated.
operating system automatically assigns an available connection. If no more connection
resources are available, the engineering station cannot communicate online with the
CPU.
configuration, it is assigned to this HMI station, that is, it only needs to be allocated.
operating system automatically assigns an available connection. If no more connection
resources are available, the HMI station cannot communicate online with the CPU.
WinCC
) according to the following rules:
Communication
4.3 S7 connections
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