Rs232/Rs485 Interface; Table 5 X101 Rs232/Rs485 Interface, Pin Assignment; Fig. 4 X101 Rs232/Rs485 Interface - Beckhoff CX8180 Manual

4.4

RS232/RS485 interface

Two serial interfaces are wired on the D-Sub socket: one with RS232 and one with RS485 physics. Both
interfaces have the same potential and are electrically isolated from the CPU. The interfaces can be used
simultaneously and work independently of each other.
Fig. 4: X101 RS232/RS485 interface
Observe the PIN assignment of the D-Sub socket when assembling cables for wiring. The ZB3180 connector
with two cable outlets can be used for wiring (see: D-sub connector ZB3180 [} 65]).
Table 5: X101 RS232/RS485 interface, PIN assignment.
PIN
1
2
3
4
5
6
7
8
9
Termination resistor
Usually, no termination resistors are required for low baud rates. A termination resistor can lead to an
improved transmission level in cases where long lines, a high line resistance, a large number of RS485
devices and/or high baud rates are used. RS485 is implemented in different ways, and it is not necessarily
clear whether a termination resistor improves or impairs the result.
Our recommendation is to use an active termination resistor (PIN4 - 390 Ohm, PIN1 - 220 Ohm, PIN6 - 390
Ohm, PIN5/9). PIN4 is assigned 5 V
should only be used for the termination resistor. Do not operate any other electrical components on PIN4,
otherwise the CX8180 may be destroyed.
CX8180
Meaning
RS485
RxD (RS232)
TxD (RS232)
+ 5 V
GND
RS485
RTS (RS232)
CTS (RS232)
GND
and PIN5/9 GND for the active termination resistor (RS485). PIN4
DC
Version: 1.5
Description
(+)
Signal in
Signal out
+
Ground
(-)
Signal out
Signal in
Ground
Product overview
Signal
A
Receive Data
Transmit Data
Vcc
Ground
B
Request to Send
Clear to Send
Ground
17