Siemens SIMATIC NET PROFIBUS User Manual

PROFIBUS NETWORKS
1-10
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
1.2.4 Transmission Techniques According to EIA Standard RS-485
EIA Standard RS-485
The RS-485 transmission technique corresponds to balanced data transmission as
specified in the EIA Standard RS-485 /4/. This transmission technique is
mandatory in the PROFIBUS standard EN 50170 for data transmission on twisted
pair cables.
The medium is a shielded, twisted pair cable.
The bus cable is terminated at both ends with the characteristic impedance. Such
a terminated bus cable is known as a segment.
The attachment of the node to the bus is via a bus terminal with a tap line or a bus
connector (maximum 32 nodes per segment). The individual segments are
interconnected by repeaters.
The maximum length of a segment depends on the following:
S The transmission rate
S The type of cable being used
Advantages:
S Flexible bus or tree structure with repeaters, bus terminals, and bus connectors
for attaching PROFIBUS nodes
S Purely passive passing on of signals allows nodes to be deactivated without
affecting the network (except for the nodes that supply power to the terminating
resistors)
S Simple installation of the bus cable without specialized experience.

Siemens SIMATIC NET PROFIBUS Specifications

General

Brand	Siemens
Model	SIMATIC NET PROFIBUS
Category	Network Hardware
Language	English