User Guide
11
3.3.3 RS-485 half duplex wiring example
3.3.4 RS-485 internal circuit diagram
RS-485 0V
RS-485_Z
RS-485_Y
RS-485_B
RS-485_A
R
To logger
RS-485
equipment
100R or higher
(Termination resistor may not be
needed for many applications)
C1
C2
C3
G
+12V
G
RX - A
CTS - B
RTS - Y
TX - Z
0V
Z
Y
B
A
1
2
3
4
5
6
7
8
9
10
-
11
12
13
14
15
22R
22R
22R
22R
R
R
External
Internal
100R or higher *
100R or higher *
* Note the external termination resistors are optional. Some applications can use much higher
value resistors and some may not need resistors at all depending on the distance and wire quality
involved.
If the termination resistor is primarily needed for i mpedance matching then a value matching the
line resistance will have to be used, i.e. 100R
100R
0V
0V
A
B
Y
Z
RX
TX
