Connecting
7.8 PROFIBUS / MPI
NCU 7x0.2
70 Manual, 02/2011, 6FC5397-0AP20-0BA0
7.8.6 Disconnecting stations from the PROFIBUS
Removing the bus connector
You can remove the bus connector with a looped-through bus cable from the PROFIBUS DP
interface at any time without interrupting data traffic on the bus.
CAUTION
Data exchange on the bus can be interrupted!
A bus segment must always be terminated with the terminating resistor at both ends. This
is not the case, for example, if the last node with a bus connector is de-energized. Because
the bus connector takes its voltage from the node, this terminating resistor is ineffective.
Make sure that the nodes at which the terminating resistor is connected are always
energized.
7.8.7 Operating the X136 interface as MPI
Applications
The X136 interface can also be operated as an MPI interface instead of a PROFIBUS DP
interface. The typical (default) baud rate is 187.5 Kbaud. A baud rate of up to 12 MBaud can
be set for communication with other CPUs. It should be noted, however, that a rate of
12 MBaud is not supported by all CPUs (e.g. smaller SIMATIC S7 CPUs).
The following list provides examples of when using MPI (multi-point interface) may prove
effective:
● If a PC/PG with an MPI is being used
● If an MPI-type handheld unit is being used
Operate MPI like PROFIBUS
The information on wiring the connector (terminating resistors) for PROFIBUS and the rules
on the laying of cables for PROFIBUS apply to this interface as well. When carrying out this
procedure, consult the relevant references.
Connector features
The bus connector is used to connect the MPI bus cable to the MPI (X136). This enables
you to establish connections to additional nodes (e.g. PG or SIMATIC S7-CPU). Only bus
connectors with a 35° cable outlet should be used in order to ensure that the front cover can
be closed.
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