Siemens SIMATIC C7-626, Installation, Assembly, Wiring

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3
3-7
C7-626 / C7-626 DP Control Systems
C79000-G7076-C626-01
The MPI addresses set at the factory should not be assigned as fixed node
addresses since, otherwise, address conflicts (double MPI addresses) can
arise when devices are replaced or the network is expanded.
S
Reserve the MPI address “0” for a service programming device.
S
Reserve the address “1” for the C7 OP.
S
Reserve the address “2” for the C7 CPU.
This avoids double assignment of MPI addresses after installing a further
preset C7 or S7-300 in the MPI network (for example, when replacing a C7).
Reserve the L2 address “0” for a service programming device which may be
temporarily connected to the L2-DP network at a later stage if required. You
should therefore assign other L2 addresses to the programming devices
included in the L2-DP network.
You connect the individual nodes via the bus connectors and the PROFIBUS
bus cable. Remember to provide for the nodes a bus connector with
programming device socket to which a programming device can be
connected if required (see also Section 3.5).
Use the RS 485 repeater for connections between segments or for extending
cables.
See the reference manual /71/ for details of how to install and use a repeater.
A cable must be terminated with a surge impedance. To do this, switch on the
terminating resistance at the first and last node of the network.
At least one of these two nodes must be supplied with power.
Figure 3-2 shows you where to connect the terminating resistance on the bus
connector.
on
off
Terminating
resistance
switched off
on
off
Terminating
resistance
switched on
Figure 3-2 Terminating Resistance on the Bus Connector
Recommendation
for MPI Addresses
in the Network
Recommendation
for PROFIBUS
Addresses
Components
Using the RS 485
Repeater
Terminating
Resistance
Terminating
Resistance On Bus
Connector
Configuring MPI Networks and PROFIBUS-DP Networks