5. External connections
5.7 Profibus interface
5.7.0.2 Profibus topology
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A bus segment can interconnect up to 32 slaves.
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Several bus segments can be connected using repeaters (bi-directional amplifiers).
The use of repeaters enables the maximum cable length to be
increased.
For more details, please consult the documentation for repeaters
provided by manufacturer.
Only use bus connector plugs specified for use with PROFIBUS networks.
These plugs combine both bus cables on a node and ensure that the cable shield has a
low-impedance connection to the node's shield reference potential.
In addition, these bus connector plugs include a PROFIBUS-specific cable termination
that can be activated if necessary.
A bus segment must be provided with cable termination at both ends. This termination
is passive, but is fed from the node. It ensures a defined quiescent signal on the bus if
no bus station is sending. These bus terminations are preferably implemented extern-
ally in the connector housing as per the PROFIBUS standard (and can be implemented
using the aforementioned bus connector plugs).
Figure 31: Profibus bus segment with four nodes
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The bus segment must be terminated at both ends.
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No more than two terminations must be provided for each bus
segment.
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At least one of the two terminations must be fed by the bus sta-
tion.
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Operation without correct termination of the Profibus network can
cause transfer errors.
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12/15 MN048017 EN www.eaton.eu
