ITEM C 3-Series, Product Manual

Page: 156 / 160

Technology modules
Page 156
12.1.4 Termination and bus terminating resistors
All of the bus segments of a PROFIBUS network must be equipped with bus terminating resistors to minimise line reflections
and to adjust a defined rest potential on the line. The bus termination must be provided at the beginning and at the end of
every bus segment.
Most PROFIBUS connectors come supplied with integrated terminating resistors. For bus connections with connectors without
integrated terminating resistors, the PROFIBUS-DP interface has its own terminating resistors. They can be activated with the
help of the two DIP switches on the module (switch set to ON).
To ensure safe operation of the network, only one bus termination may be used at a time.
The external connection can also be set up discretely (see
Figure 31
). The 5 V power supply that is required for the externally
connected terminating resistors is supplied at the PROFIBUS connector of the PROFIBUS-DP interface (see the pin assignment
in
Table 53
).
GND 5 V
+5 V
A-Line
B-Line
390 Ohm
220 Ohm
390 Ohm
Figure 31: PROFIBUS-DP interface: connection with external terminating resistors