CX2020-N031-0003 BECKHOFF Basic CPU Module RS485 Interface

Product Overview

The CX2020-N031-0003 (CX2020-N031-0003) is a specialized Basic CPU module within the Beckhoff CX2000 Embedded PC series, currently in the service phase of its lifecycle. This unit is specifically configured with an integrated RS485 interface, utilizing a standard 9-pin D-sub socket for serial communication. Engineered for high-performance automation tasks, the CX2020-N031-0003 serves as a rugged industrial controller capable of managing complex PLC and Motion Control applications while facilitating legacy communication with field devices. Its configuration as a "drop point" with "echo" capability and internal termination set to "off" makes it a precise replacement or expansion component for established industrial networks in manufacturing, building automation, and energy management.

Technical Configuration

The hardware architecture of the CX2020-N031-0003 is optimized for serial connectivity within a bus topology. The 9-pin D-sub RS485 interface is factory-set for specific network behaviors: it operates as a drop point, meaning it is intended to be connected along a multi-drop bus rather than at the end of a line. The "with echo" setting ensures that the transmitted data is reflected back to the receiver for verification purposes, a common requirement in certain legacy industrial protocols. Additionally, the internal termination resistor is disabled (off), allowing engineers to apply external termination at the physical ends of the network segment as per standard RS485 installation practices.

Technical Specifications

Technical FAQs

What does the "Service Phase" status mean for this module?

The service phase indicates that the product is no longer recommended for new designs but is fully supported for maintenance, repair, and replacement in existing installations. This ensures that B2B customers can maintain their machinery without needing to redesign the entire control architecture.

How should the RS485 pinning be handled for the 9-pin D-sub?

For standard Beckhoff RS485 configurations, Pin 3 and Pin 8 are typically used for Data B (+) and Data A (-) respectively. However, always refer to the specific circuit diagram for the CX2020 series to ensure compatibility with your existing serial cabling and shield grounding requirements.

Can I enable the internal termination via software?

No. In this specific N031-0003 configuration, the termination is physically "off." If this CPU module is located at either physical end of the RS485 bus, you must use a D-sub connector with a built-in, switchable termination resistor to ensure signal stability and prevent reflections.

Engineering & Installation Guide

• Bus Topology Management: Since the CX2020-N031-0003 is configured as a drop point, ensure that the "stubs" (the distance from the main trunk line to the CPU) are kept as short as possible. Long stubs in RS485 networks can introduce significant signal distortion and communication errors at higher baud rates.

• Echo Logic Handling: Because the "Echo" feature is enabled, your PLC communication blocks or serial driver must be programmed to handle the fact that every character sent will be immediately received back by the CPU. This is often used for hardware-level collision detection but requires specific buffer management in the application software.

• Grounding and Shielding: To prevent data loss in high-interference environments (near VFDs or heavy motors), use high-quality shielded twisted-pair (STP) cabling. Connect the cable shield to the metal shell of the D-sub connector to provide a low-impedance path for electromagnetic noise to reach the system ground.