Omron CS1W-PRM21 Operation Manual page 49

Setting up a Network
Cable Type
Maximum PROFIBUS
Cable Length
Stub Lines
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:
Characteristic
Impedance
Capacitance per unit length
Loop resistance
Core diameter
Core cross section
Note The PROFIBUS standard EN 50170 also specifies a Type B cable with slightly
different cable characteristics. This Type B cable is no longer recommended
for use.
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.
Baud rate
(kbit/s)
9.6
19.2
45.45
93.75
187.5
Note If the network must be extended beyond the range of the advised cable
length, the use of a fibre optic segment to cross the larger distance should be
considered.
Passive Stub lines (branches from the main line) should be avoided for data
transmission speeds of more than 500 kbit/s. Except at end stations with ter-
mination, it is recommended to always use plug connectors that permit two
data cables to be connected directly to the plug. This method allows the bus
connector to be plugged and unplugged at all times without interrupting data
communication between other stations.
Distance/segment Baud rate
(m)
1200
1200
1200
1200
1000
Section 2-4
Value
135 - 165 ohms
< 30 pF/m
110 ohms/km
0.64 mm
2
0.34 mm
Distance/segment
(kbit/s) (m)
500 400
1500 200
3000 100
6000 100
12000 100
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