Omron CJ1W-PRT21 Operation Manual page 65

 Tree Topology
The use of repeaters allows the extension of three or more Linear Bus segments into a tree topol-
ogy. In a tree topology more than three repeaters are allowed, provided that there are no more than
three repeaters between any two devices in the network. The following figure presents an example
of a network with more than three segments and repeaters
M / S
Segment 4
Max. 31 stations
M / S
M / S
Max. total number of stations = 126
 Cable Type
The PROFIBUS standard EN 50170 specifies Type A shielded, twisted-pair cable as the recom-
mended cable type for use in an RS-485 based PROFIBUS network. This cable type has the follow-
ing 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 different cable char-
acteristics. 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.
CJ-series PROFIBUS Slave Unit Operation Manual for NJ-series CPU Unit (W510)
Segment 1
Max. 31 stations
R
Max. 28 stations
R
Segment 5
Max. 30 stations
Master or slave station
R
Repeater
Termination
135 - 165 Ωs
< 30pF/m
110 Ω/km
0.64 mm
0.34 mm 2
2 Nomenclature and Installation
Segment 2
Max. 31 stations
Segment 3
R
R
M / S
R
Segment 6
Max. 31 stations
Value
M / S
M / S
M / S
2-9
2