3-2
C7-621 / C7-621 AS-i Control Systems
C79000-G7076-C621-01
3.1 Communication via the MPI Interface
The C7 interface for connecting devices such as programming devices is
known as the Multipoint Interface since several devices at different locations
(points) can communicate with the C7 via this interface.
The transmission rate of the C7 is fixed at 187.5 Kbps.
You can create an MPI network by interconnecting the following devices:
S Programming devices (PG/PC)
S Operator interface systems (OPs)
S S7-300 / M7-300
S S7-400 / M7-400
S Further C7s
S FMs, CPs
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:
– One for the C7 CPU
– One for the C7 OP
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)
You can interconnect up to 126 (addressable) nodes on an MPI network.
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.
Definition:
Multipoint
Interface MPI
Transmission Rate
Connectable
Devices
Device/Node
Segment
Number of Nodes
MPI Addresses
Configuring an MPI Network
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