Siemens SINUMERIK ONE NCU 1740, Руководство по эксплуатации оборудования

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Connector features
The bus connector connects the PROFIBUS cables to the PROFIBUS DP interface X126, thus
establishing a connection to additional nodes.
Only bus connectors with a 35° cable outlet should be used in order to ensure that the front cover
can be closed.
8.9.3 Connection components in PROFIBUS
Connection components
Individual nodes are connected by means of bus connectors and PROFIBUS cables. Remember
to provide a bus connector with a programming port at either end of the subnet. This will give
you the option of expanding the subnet if required, for example, for a programming device.
Use RS 485 repeaters to connect segments or extend cable lengths.
Segments
A segment is a bus line between two terminating resistors. A segment may 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 on a subnet or segment.
The NCU must be either the first or the last node on the subnet.
Make sure that the stations to which the terminating resistor is connected are always supplied
with voltage during power-up and operation.
8.9.4 Rules for the laying of PROFIBUS cables
Laying of bus cables
During laying of the PROFIBUS cable, you must avoid:
• twisting
• stretching and
• squeezing
Connecting
8.9 PROFIBUS DP
NCU 1740
76
Equipment Manual, 10/2021, A5E51087503B AA