Siemens SIMATIC ET 200S Manual page 142

Functions of the IM 151-7 CPU
Assigning S7 connections
The S7 connections on a communications-capable module can be assigned in
various ways:
Reserving connections during configuration
S If, in STEP 7, a CPU is plugged in when the hardware is configured, S7
connections are automatically reserved on this CPU for both the PD and OP
communication.
S For PD and OP communication and for S7 basic communication, the S7
connections can be reserved in STEP 7.
Assigning connections by programming
For the S7 basic communication, the connection is established via the user
program. The CPU operating system initiates the build up of the connection and
the corresponding S7 connections are assigned.
Assigning connections upon commissioning, testing and diagnosis
S7 connections for the PD communication are assigned by means of an online
function on the Engineering Station (PD/PC with STEP 7):
S If an S7 connection was reserved in the CPU for PD communication when the
hardware was configured, it is allocated to the Engineering Station, i.e. it is
simply assigned.
S If all reserved S7 connections for PD communication have already been
assigned and unreserved S7 connections are still fee, the operating system
allocates a connection that is still free. If there are no longer any free
connections, the Engineering Station cannot communicate online with the CPU.
Assigning connections for B&B utilities
S7 connections for the OP communication are assigned by means of an online
function on the B&B Station (OP/TP/... with ProTool):
S If an S7 connection was reserved in the CPU for OP communication when the
hardware was configured, it is allocated to the B&B Station, i.e. it is simply
assigned.
S If all reserved S7 connections for OP communication have already been
assigned and unreserved S7 connections are still fee, the operating system
allocates a connection that is still free. If there are no longer any free
connections, the B&B Station cannot communicate online with the CPU.
8-30
ET 200S IM 151-7 CPU Interface Module
A5E00058783-04