Figure 4-2 Block Diagram: General Topology Of The Twisted-Pair Cable; Figure 4-3 Terminal Assignment - Siemens SENTRON PAC RS485 Manual

Assembling
4.4 Connecting
Figure 4-2
+/B
-/A
COM
TER
PU
PD
Figure 4-3
1. Connect the cables to the appropriate screw terminals on the terminal block. You can find
2. Connect the cable shield at one end with protective ground PE.
3. Connect the signal Common with protective ground. This grounds the expansion module.
4. On the first and last communication nodes, switch a bus terminating resistor between the
24
Block diagram: General topology of the twisted-pair cable
B signal; D1
A signal; D0
Common = Ground
(Line) Termination = bus terminating resistor
Pull-up resistor
Pull-down resistor
Terminal assignment
the assignments of the terminals in the figure "Terminal assignment".
positive signal and the negative signal. A 120-Ohm bus terminating resistor is
implemented in the PAC RS485 expansion module for this purpose. In the case of other
values, use an external bus terminating resistor. Attach this to the first and last
communication node.
PAC RS485
Manual, 02/2008, A5E02091800B-01