Siemens SENTRON PAC RS485 - Figure 4-4 Terminal Assignment with Terminating Resistor; Figure 4-5 Terminal Assignment with Line Polarization

Assembling
4.4 Connecting
PAC RS485
Manual, 02/2008, A5E02091800B-01
25
&RP % $ 7HU 38 3'
Figure 4-4 Terminal assignment with terminating resistor
NOTICE
Incorrect bus terminator
If you switch more than two bus terminating resistors on one bus, this can result, for
example, in signal reflections that interfere with communication on the bus.
Never attach more than two bus terminators to one bus. Attach one bus terminating
resistor at the start of the bus and one terminating resistor at the end of the bus.
5. Make sure that there is sufficient strain relief for the connected cables.
Line polarization
A resistor for line polarization is implemented in the terminal block.
&RP % $ 7HU 38 3'
Figure 4-5 Terminal assignment with line polarization
If one or more communication nodes require line polarization, switch a resistor pair PU and
PD on the RS 485 twisted-pair cable in the case of a PAC RS485 expansion module. To do
so, switch on the resistor in the terminal block of the relevant PAC RS485 expansion module
shown in the figure "Terminal assignment with line polarization".
See also
Assembly (Page 21)
Communication interface (Page 70)