Communication with the S7-300
5.4 S7 communication structure
5.4.2 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
• If a CPU is inserted when the hardware is configured with
STEP 7
, two S7 connections,
one for PG and one for OP communication, are automatically reserved on the CPU.
• It is possible to reserve S7 connections in
STEP 7
for PG / OP communication and S7
basic communication.
Assigning connections in the program
In the case of S7 basic communication, the connection is set up by the user program. The
CPU operating system initiates connection setup and the relevant S7 connections are
assigned.
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:
• An S7 connection resource for PG communication which was reserved in your CPU
hardware configuration is assigned to the engineering station, that is, it only needs to be
allocated.
• If all reserved S7 connection resources for PG communication are allocated, the
operating system assigns a free S7 connection resource which has not yet been
reserved. If no more connection resources are available, the engineering station cannot
go online to the CPU.
Allocating connection resources to OCMS services
An online function of the OCM station (OP/TD/... with
ProTool
) allocates S7 connection
resources for OP communication:
• An S7 connection resource for OP communication you have reserved in your CPU
hardware configuration is therefore assigned to the OCM station engineering station, that
is, it only needs to be allocated.
• If all reserved S7 connection resources for OP communication are allocated, the
operating system assigns a free S7 connection resource which has not yet been
reserved. If no more connection resources are available, the OCM station cannot go
online to the CPU.
S7-300 CPU Data: CPU 315T-2 DP
Manual, 12/2005, A5E00427933-02
5-15
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