Components For Transmission Rates Up To 1.5 Mbps - Siemens SIMATIC NET PROFIBUS Owner's Manual

Connecting Segments Using RS-485 Repeaters
By using RS-485 repeaters, segments can be interconnected. The RS-485
repeater amplifies the data signals on the LAN cables. You require an RS-485
repeater when you want to attach more than 32 nodes to a network or when the
permitted segment length is exceeded. A maximum of 9 repeaters can be used
between any two nodes. Both bus and tree structures can be implemented.
Figure 2-1 shows a typical topology using the RS-485 technique with 3 segments
and 2 repeaters.
S7-400
OP 25
À
OP 25
À
À Terminating resistor activated
Á PG attached via tap line (6ES7 901-4BD00-0XA0)
for maintenance purposes
Figure 2-1 Topology Using the RS-485 Technique
Increasing the overall span of a network by using repeaters can lead to longer
transmission times that may need to be taken into account when configuring the
network (see Chapter 3).
2.1.1

Components for Transmission Rates up to 1.5 Mbps

All SIMATIC NET bus attachment components can be used for transmission rates
1.5 Mbps.
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
Topologies of SIMATIC NET PROFIBUS Networks
S7-300 S7-300
PG
Tap line
Á
S7-400
OP 25
PG
À
S7-400
RS-485
repeater
À
À
RS-485
repeater
À
2-3