25
Setting up a PROFIBUS Network
Section 2-4
Cable Type
The PROFIBUS standard EN 50170 specifies Type A shielded, twisted- pair
cable as the recommended cable type for use in an RS-485 based PROFI-
BUS network. This cable type has the following characteristics:
Note
The PROFIBUS standard EN 50170 also specifies a Type B cable with differ-
ent cable characteristics. Use of Type B cable is no longer recommended.
Maximum PROFIBUS
Cable Length
The transmission speed defines the maximum advised cable distance or
cable segment in metres before the use of a repeater is recommended. The
cable lengths specified in the following table are based on PROFIBUS type A
cable.
Note
If network extension beyond the range of the advised cable length is required,
the use of fibre optic cable to cross the larger distance should be considered.
Stub Lines
Passive Stub lines (branches from the main line) should be avoided for data
transmission speeds of more than 500 kbit/s. Except at end devices with ter-
mination, it is recommended to always use plug connectors that permit two
Segment 1
Max. 31 stations
Segment 2
Max. 31 stations
M / S
M / S
M / S
M / S
Segment 3
Max. 28 stations
Segment 4
Max. 31 stations
Segment 5
Max. 30 stations
Segment 6
Max. 31 stations
M / S
R
R
R
R
M / S
R
Master or slave station
Repeater
Termination
Max. total number of stations = 126
M / S
R
Characteristic
Value
Impedance
135 - 165 ohms
Capacitance per unit length
< 30 pF/m
Loop resistance
110 ohms/km
Core diameter
0.64 mm
Core cross section
0.34 mm
2
Baud rate
(kbit/s)
Distance/segment
(m)
Baud rate
(kbit/s)
Distance/segment
(m)
9.6
1200
500
400
19.2
1200
1500
200
45.45
1200
3000
100
93.75
1200
6000
100
187.5
1000
12000
100
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