Siemens SIMATIC NET PROFIBUS Point-to-Multipoint Link, Point-to-Point Link with Two Profibus ILMs

Topologies of SIMATIC NET PROFIBUS Networks

Master OP 25

À

Master

PG/PC/OP

2

2

ILM

Infrared link

0.5 to 15 m

À

Slave

ET 200M

ILM

2

2

Master

S7-400

À

PROFIBUS

master network segment

PROFIBUS

slave network segment

Slave

ET 200S

2

À

ÀTerminating resistor activated

2 LAN cable for PROFIBUS

Figure 2-9 Point-to-Point Link with Two PROFIBUS ILMs

Figure 2-9 illustrates the typical structure of a PROFIBUS network with master and slave nodes and an infrared link with two PROFIBUS ILMs. The infrared link is implemented as a point-to-point link between the two PROFIBUS ILMs. The two PROFIBUS ILMs replace a cable connection between the two network segments. Remember that only slave nodes are permitted in the slave network segment.

Point-to-Multipoint Link

Several ILMs are positioned opposite to a single ILM so that several ILMs are in the infrared light cone of another ILM. Only the ILMs positioned opposite each other can exchange data. A data exchange between adjacent ILMs is only possible by using a surface that reflects infrared light. If you consider this option, remember that the length of the link is the path from the ILM to the reflector and from the reflector to the partner ILM. Signal attenuation will also occur since the reflector can only reflect part of the infrared light to the partner ILM. Such losses mean a reduction in the maximum length of a link.

PROFIBUS Networks SIMATIC NET	2-15
6GK1970-5CA20-0AA1 Release 2 05/2000