Setting Up A Profibus-Dp Network; Fieldbus Cabling - Omron PRT1-COM Operation Manual

Setting up a PROFIBUS-DP network

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Setting up a PROFIBUS-DP network

2-3-1 Fieldbus cabling

Bus structure
Cable type
Cable
Maximum length
Stub lines
Fieldbus connector
18
All PROFIBUS-DP devices are connected in a line structure. Each RS485 bus
segment may contain up to 32 stations (masters, slaves, repeaters). When more
than 32 stations are required, repeaters must be used to link the individual bus
segments. The bus must be terminated at the beginning and at the end of each
segment.
The standard EN50170-2 specifies the use of shielded twisted pair cables with
the following parameters (PROFIBUS-DP line type A):
PROFIBUS-DP Cable parameters
Parameter
Impedance
Capacitance per unit length
Loop resistance
Core diameter
Core cross section
The PROFIBUS-DP User Group recommends the following colour coding for
the data signal lines:
A-line - green
B-line - red
The maximum length of the cable depends on the transmission speed. The
cable lengths specified in the table below are based on the above cable
specifications.
Cable length vs. Baud rate
Baud rate (kbit/s)
9.6, 19.2, 45.45, 93.75
187.5
500
1500
3000, 6000, 12000
Stub lines should be avoided for data transmission speeds of more than 500 kbit/s.
Plug connectors available on the market permit the incoming data cable and the
outgoing data cable to be connected directly in the plug connector. This means
that stub lines do not have to be used, and the bus plug connector can be
connected and disconnected at all times without interrupting data
communication with the other stations.
The connector plug to connect to the PRT1-COM is a 9-pin male sub-D
connector, preferably with a metal case, conducting screws and a solder lip for
connecting the shield of the cable. The cable should at least be connected to pin
3 (B-line) and pin 8 (A-line) of the connector.
Section
Value
135 to 165 Ω (3~20 MHz)
< 30 pF/m
< 110 Ω/km
> 0.64 mm
2
> 0.34 mm (22 AWG)
length/segment (m)
1200
1000
400
200
100
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