Communication Via The Mpi Interface - Siemens simatic c7-621 Hardware Installation Manual

Configuring an MPI Network
3.1

Communication via the MPI Interface

Definition:
The C7 interface for connecting devices such as programming devices is
Multipoint
known as the Multipoint Interface since several devices at different locations
Interface MPI
(points) can communicate with the C7 via this interface.
Transmission Rate The transmission rate of the C7 is fixed at 187.5 Kbps.
Connectable You can create an MPI network by interconnecting the following devices:
Devices
Device/Node
Convention: In the following sections, all the devices interconnected on an
MPI network will be called nodes. Please note that the C7 itself occupies two
MPI addresses and therefore represents two nodes, as follows:
Segment A segment is a section of the network between two terminating resistors. A
segment can include up to 32 nodes. A segment is also limited by the
maximum permitted cable length that depends on the transmission rate (see
Section 3.3)
Number of Nodes You can interconnect up to 126 (addressable) nodes on an MPI network.
MPI Addresses To allow all the nodes connected to the MPI network to communicate with
each other, you must assign an MPI address to each node and you must also
set a highest MPI address. Before you network the nodes, you must assign the
MPI addresses individually on a programming device.
Note
The RS 485 repeater is not assigned an MPI address.
3-2
Programming devices (PG/PC)
Operator interface systems (OPs)
S7-300 / M7-300
S7-400 / M7-400
Further C7s
FMs, CPs
– One for the C7 CPU
– One for the C7 OP
C7-621 / C7-621 AS-i Control Systems
C79000-G7076-C621-01