5 Installation
5.3 Interfaces
44
MICRO PANEL XV-152
12/2011 MN04802006Z-EN
www.eaton.com
Wiring
Shielded twisted pair cables must be used.
Tab. 24 Cable specifications
RS485 topology
A bus segment can connect up to 32 bus stations.
Several bus segments can be linked via repeaters (bidirectional amplifiers). Refer to the documen-
tation of the repeater manufacturer for further information.
A bus segment must be provided with cable termination (120
Ω
) at both ends. These terminations
must be connected directly between pin 3 and 7 in the connector.
Cable specifications
Rated surge impedance
120
Ω
Permissible surge impedance
108…132
Ω
Max. cable length
1200 m
Possible baud rates
9600 Bit/s
19200 Bit/s
38400 Bit/s
57600 Bit/s
115200 Bit/s
When preparing the cables, ensure that there is a low-resistance connection between
the cable shield and the connector casing (
→
Chapter 5.3.2,
25).
The maximum cable length can be increased by using repeaters. Refer to the documen-
tation of the repeater manufacturer for further information.
The bus segment must be terminated at both ends.
No more than two terminations must be provided on each bus segment.
Transmission faults can occur if operation is carried out without the correct termina-
tion.
Fig. 22 Bus segment with four bus stations
1
2
3
6
7
5
4
8
9
120
1
2
3
6
7
5
4
8
9
120
1
2
3
6
7
5
4
8
9
1
2
3
6
7
5
4
8
9
GND
A
B
GND
A
B
GND
A
B
GND
A
B
GND
A
B
GND
A
B
