Siemens SIMATIC NET PROFIBUS manual Passive Components for RS-485 Networks

Passive Components for RS-485 Networks

Note

The shield clamps are used solely to contact the shields and are not suitable as strain-relief clamps. This means that the LAN cables must be secured as close as possible to the bus terminals to provide mechanical strain relief.

Note

Bus terminals installed at the end of segments require the 5 V power supply from the DTE interface to supply the activated, integrated terminating resistor.

The sub-D male connector must therefore always be plugged in and secured by screws. The attached DTE must not be turned off.

Note

The same wires (green or red must always be connected to the same terminal A or B in all bus terminals and with all bus connections) and be uniform throughout the segment.

The following scheme is recommended for a PROFIBUS network:

Terminal A: green wire

Terminal B: red wire

Note

Notes on the 12M bus terminal

The 12M bus terminal must only be plugged in to an interface with the power turned off.

At the ends of a segment, the PROFIBUS cable must only be connected to terminal pair A1, B1. Terminals A2, B2 are disconnected from the bus when the terminating resistor is activated.

PROFIBUS Networks SIMATIC NET	4-57
6GK1970-5CA20-0AA1 Release 2 05/2000