I/O Terminal /
MOUNTING AND WIRING
23
Note:
In systems with more than two stations all devices are wired in parallel. It is essential
that the bus cables are terminated with resistors at the conductor ends in order to avoid
reflections and associated transmission problems.
3.6.3 Distances
The bus cable is specified in EN 50170. This yields the following lengths for a bus segment.
Baud Rate in kbits/sec 9.6
19.2
93.75
187.5
500
1500
12000
Cable length in m
1200
1200
1200
1000
400
200
100
Stubs up to 1500 kbaud <6.6 m; at 12 Mbaud stub segments should not be used.
3.6.4 Bus
Segments
A bus segment consists of at most 32 devices. 126 devices are permitted in a Profibus
network. Repeaters are required to refresh the signal in order to achieve this number. Each
repeater is counted as one device.
IP-Link is the subsidiary bus system for Fieldbus Boxes, whose topology is a ring structure.
There is an IP master in the coupler modules to which up to 120 extension modules may be
connected. The distance between two modules may not exceed 5 m. When planning and
installing the modules, remember that because of the ring structure the IP-Link master must
be connected again to the last module.
3.6.5 Installation
Guidelines
When assembling the modules and laying the cables, observe the technical guidelines
provided by the Profibus User Organization for Profibus DP/FMS (see www.profibus.com).