5 Installation
5.3 Interfaces
48
HMI/PLC XV-102
08/2016 MN04802004Z-EN
www.eaton.com
Profibus topology
A bus segment can interconnect up to 32 slaves.
Several bus segments can be connected using repeaters (bi-directional amplifiers). Refer to the
documentation of the repeater manufacturer for more specific details.
Only use bus terminal connectors that are specified for use in the Profibus network. They hold both
bus cables on a bus station and ensure a low impedance connection of the cable screen to the
shield reference potential of the bus station. These bus terminal connectors contain the Profibus
cable termination that can be switched on as required.
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 should be implemented externally in the connector casing
according to the Profibus standard (they can also be implemented with the bus terminating
connector described above).
The use of repeaters enables the maximum cable length to be increased. Refer to the
documentation of the repeater manufacturer for more specific details.
Fig.. 24 Bus segment with four nodes
The bus segment must be terminated at both ends.
No more than two terminations must be provided for each bus segment.
At least one of the two terminations must be fed by the bus station.
Operation without correct termination of the Profibus network can cause transfer er-
rors.
1
2
3
6
7
5
4
8
9
390
390
1
2
3
6
7
5
4
8
9
1
2
3
6
7
5
4
8
9
1
2
3
6
7
5
4
8
9
M5EXT
(GND)
A
B
M5EXT
(GND)
A
B
M5EXT
(GND)
A
B
M5EXT
(GND)
A
B
M5EXT
(GND)
A
B
M5EXT
(GND)
A
B
220
220
390
390
