4.7 Connecting PROFIBUS/MPI
4.7.1
PROFIBUS connection components
Connection components
Individual nodes are connected by means of bus connectors and PROFIBUS cable.
Remember to provide a bus connector with a programming port at the ends of the subnet. This
will give you the option of expanding the subnet if required (for example, for a programming
device or SIMATIC HMI device).
Use RS 485 repeaters for the connection between segments and to extend the cable.
Segments
A segment is a bus cable between two terminating resistors. A segment can contain up to 32
nodes. In addition, a segment is limited by the permissible cable length, which varies according
to the transmission rate.
Terminating resistor
A cable must be terminated with its own surge impedance to prevent line disturbances caused
by reflections. Activate the terminating resistor at the first and last node of a subnet or segment.
Make sure that the nodes to which the terminating resistor is connected are always supplied
with voltage during power-up and operation.
4.7.2 PROFIBUS cables and connectors
Properties of PROFIBUS cables
The PROFIBUS cable is a two-core, twisted and shielded cable with defined properties:
Properties of the cables
Table 4-4 Properties of PROFIBUS cables
Characteristics Values
Characteristic impedance Approximately 135 to 160 Ω (f = 3 to 20 MHz)
Loop resistance ≤ 115 Ω/km
Effective capacitance 30 nF/km
Damping 0.9 dB/100 m (f = 200 kHz)
Permissible conductor cross-section 0.3 mm
2
to 0.5 mm
2
Permissible cable diameter 8 mm + 0.5 mm
Connecting
4.7 Connecting PROFIBUS/MPI
SIMOTION D4x5-2
76 Commissioning and Hardware Installation Manual, 03/2018, A5E33441636B
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