Technical data

www.westermo.com Theoretical and general applications 59
ed in applications exposed to electromagnetic interference, between installation sites
with different ground potential and to bridge large distances.
Network topology PROFIBUS
As the basic interface is RS-485 devices should be connected in a bus structure. Up to
32 stations can be connected to a segment. Active bus termination is connected at the
beginning and end of each segment as in the figure below. Both bus terminations must
have a permanent voltage supply to give error free communication. Bus termination is
usually integrated into the connectors and is activated with a switch. A repeater is used
when more than 32 stations are to be connected to the same network, or when the
Remember that a repeater puts an electrical load on the network so you can only
have 31 stations in a segment with a repeater. Up to 10 segments in a row can be
interconnected when using regenerating repeaters.
(3) RxD/TxD -P
VP
390 R
RxD/TxD -P
220 R
390 R
GND
(5) GDND
(6) VP
(8) RxD/TxD -N
RxD/TxD -N
Data cable B
Station 1
Prodecting
earth
Prodecting
earth
Station 2
Data cable A
Bus termination
network has longer transmission distances than those stated in the table on page 58.
B A C K