BECKHOFF CX2020 - Manual (Page 33)

Mounting and wiring
3.11 RS422/RS485 connections (CX20x0­N031)
The CX20x0­N030 system interface provides an RS422 or RS 485 interface, COM1 (X300). It is
implemented on a 9­pole Sub­D socket strip. If more than one interface is required the system can be
extended via the Terminal Bus (K­ or E­bus) or Bus Terminals (KL/EL6021) which provide serial interfaces.
The pin assignment is shown at the bottom of the page.
The maximum baud rate on both channels is 115 kbit. The interface parameters are set via the operating
system or from the PLC program.
COM interface (socket)
Table 7: Pin assignment of the COM interface
PIN Signal Type Description
2 TxD+ Data­Out + Transmit 422
3 RxD+ Data­In + Receive 422
5 GND Ground Ground
6 VCC VCC +5V
7 TxD­ Data­Out ­ Transmit 422
8 RxD­ Data­In ­ Receive 422
For RS 485 pins 2 and 3 (data +) must be connected, and pins 7 and 8 (data ­).
Setting the interface parameters
The interface is parameterised as follows in the delivery condition
Table 8: RS485 without echo, end point (terminated) standard setting
Function Status
Echo on off
Echo off on
Auto send on on
Always send on off
Auto receive on on
Always receive on off
Term on on
Term on on
CX2020, CX2030, CX2040 33 Version 1.2