Networking
5-5
Automation System S7-400 Hardware and Installation
A5E00850741-01
Rules for MPI Addresses
Observe the following rules before assigning MPI addresses:
• All MPI addresses in an MPI network must be different.
• The highest possible MPI address must be equal to or higher than the highest
actual MPI address and must be set to the same value for all nodes. (Exception:
connecting a programming device to two or more nodes.)
PG / OP -- Module communication without MPI
If one of the programming devices or operator panels connected to a multipoint
interface (MPI) communicates with an S7-400 module which does not have an MPI
connection (for example, SIMATIC NET CPs, FM 456 etc.), this module can be
reached via the CPU to w hose MPI the programming device or operator panel is
connected. In this case, the CPU s imply acts as an intermediary for the transfer.
This type of connection between a programming device or operator panel and a
module only communicating via the communication bus occupies two connection
resources in the CPU.
CPU CP or FM
MPI
C bus
PG or OP
Two connection resources
occupied in the CPU
S7-400
station
One connection
resource occupied
One connection
resource occupied
Figure 5-1 Communication between Programming Device/Operator Panel and a Module
without MPI
Maximum Number of Connections via MPI
When configuring the connections of a C PU 41x via MPI, remember to include the
PG connection in the maximum number of possible c onnections.
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