Mounting and wiring
CX8030 / CX803128 Version: 1.6
Note
Pre-assembled cables from Beckhoff
Installation is made a great deal more straightforward if pre-assembled cables from Beck-
hoff are used! Wiring errors are avoided, and commissioning is more rapidly completed.
The Beckhoff range includes fieldbus cables, power supply cables, sensor cables and ac-
cessories such as terminating resistors and T-pieces. Connectors and cables for field as-
sembly are nevertheless also available.
Note
Termination resistors
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 reflec-
tions and associated transmission problems.
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.
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 (IP230x-Bxxx or IP230x-Cxxx) to which up to 120 extension modules (IExxxx)
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.
Installation guidelines
When assembling the modules and laying the cables, observe the technical guidelines provided by the
PROFIBUS User Organization (PROFIBUS Nutzerorganisation e.V.) for PROFIBUS DP/FMS
(seewww.profibus.com).
Checking the PROFIBUS wiring
A PROFIBUS cable (or a cable segment when using repeaters) can be checked with a few simple resistance
measurements. The cable should meanwhile be removed from all stations:
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