Siemens SIMATIC NET PROFIBUS manual Components for Transmission Rates up to 1.5 Mbps

Topologies of SIMATIC NET PROFIBUS Networks

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.

S7-400S7-300

OP 25

À

PG		Tap line
	Á

S7-300

PG

RS-485

repeater

À

ÀS7-400

À

S7-400

OP 25

À

OP 25

RS-485

repeater

À

ÀTerminating resistor activated

ÁPG 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).

2.1.1Components 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	2-3
6GK1970-5CA20-0AA1 Release 2 05/2000