PROFIBUS networks
1.2 Basics of the PROFIBUS network
PROFIBUS Network Manual
20 System Manual, Edition 04/2009, C79000-G8976-C124-03
The attachment of the node to the bus is via a bus terminal with a spur line or a bus
connector (maximum 32 nodes per segment). The individual segments are connected via
repeaters.
The maximum length of a segment depends on the following:
● The transmission speed
● The type of cable being used
Benefits:
● Flexible bus or tree structure with repeaters, bus terminals, and bus connectors for
attaching PROFIBUS nodes
● Purely passive forwarding of signals allows nodes to be deactivated without affecting the
network (except for the nodes that supply power to the terminating resistors)
● Simple installation of the bus cable without specialized experience.
Restrictions:
● Distance covered reduces as the transmission rate increases
● Requires additional lightning protection measures when installed outdoors
Properties of the RS485 transmission technique
The RS485 transmission technique in PROFIBUS has the following physical characteristics:
Physical characteristics of the RS485 transmission technique
Network topology: Bus, tree structure with the use of repeaters
Medium: Shielded, twisted-pair cable
Achievable segment lengths:
(depending on the cable type
see
Segments for transmission
speeds up to a maximum of 500 kbps
(Page
42))
1,000 m
For transmission speeds up to 187.5 kbps
400 m
For transmission speed up to 500 kbps
200 m
For a transmission speed of 1.5 Mbps
100 m
For transmission speeds 3, 6 and 12 Mbps
Number of repeaters connected in
series:
Max. 9
Number of nodes: Maximum 32 on one bus segment
Maximum 127 per network when using repeaters
Transmission rates: 9.6 kbps, 19.2 kbps, 45.45 kbps, 93.75 kbps, 187.5 kbps,
500 kbps, 1.5 Mbps, 3 Mbps, 6 Mbps, 12 Mbps
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