Note On The S7-400 Cpu: Connection Resources - Siemens SIMATIC NET S7-300 Manual

2 Characteristics of the Ethernet CPs
2.5.4 Removing / Inserting (Replacing Modules)
Removing and inserting the SIMATIC NET CPs for the S7-400 while the power is
on is possible without damaging the modules.
If a CP is replaced with a new CP with the same order number, the configuration
data simply needs to be downloaded again if it is not stored on the CPU (see also
CP-specific sections of this manual).
2.5.5

Note on the S7-400 CPU: Connection Resources

Note that in the S7-400 CPU, one S7 connection is reserved for a PG and a further
one for an OP (HMI = Human Machine Interface).
S Attaching the PG over MPI:
To execute ONLINE functions (for example module diagnostics) from a PG on
an S7-400 CP via the MPI interface, two connection resources (addressing of
the interface and the K-bus) are necessary on the S7-400 CPU. These two
connection resources should be taken into account in the number of S7
connections.
Example: The CPU 412-1 has sixteen free resources for S7 functions available.
If a PG is to be used for diagnostics on the S7-400 CP and is connected to the
MPI interface, two connection resources are required on the S7-400 CPU, so
that 14 connection resources remain available.
S PG connection via PROFIBUS or Industrial Ethernet
If the PG is connected to the LAN (PROFIBUS or Industrial Ethernet), in order
to execute PG functions on the S7-400 CPU and diagnostics on an S7-400 CP,
only one connection resource on the S7-400 CPU is necessary.
A -56
S7-CPs for Industrial Ethernet Configuring and Commissioning
Release 01/2007
C79000-G8976-C182-07