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The Enduring Relevance of Serial Connections: RS-232/422 & 485 in Industrial Applications

In an era dominated by wireless and Ethernet-based communication technologies, it may seem surprising that the old serial connections such as RS-232/422 and RS-485 still find extensive use in industrial applications. Although we can't find them anymore on our computers at home, there are several compelling reasons why these serial connections persist in industrial settings. This article aims to shed light on the enduring relevance of RS-232/422 and RS-485, outlining their unique characteristics that make them indispensable in diverse industrial environments.


Reliability is paramount in industrial applications, where the uninterrupted flow of data is critical for operational efficiency and safety. Serial connections like RS-232/422 and RS-485 offer excellent reliability due to their robust physical layer characteristics. These connections are less prone to interference, noise, and signal degradation, making them ideal for industrial environments characterized by electromagnetic interference (EMI) and harsh operating conditions.


One of the key advantages of RS-232/422 and RS-485 is their backward compatibility with a wide range of legacy industrial equipment. Many industrial devices, such as programmable logic controllers (PLCs), sensors, and human-machine interfaces (HMIs), still incorporate serial communication interfaces. The prevalence of these legacy systems and the cost associated with their replacement make serial connections a preferred choice to ensure seamless integration with existing infrastructure.


Serial connections offer a simple and straightforward communication protocol. The simplicity of RS-232/422 and RS-485 makes them easy to implement and troubleshoot, reducing development and maintenance costs. The absence of complex networking protocols and the straightforward point-to-point or multi-point communication topology simplifies system design and facilitates rapid deployment in industrial environments.


Industrial environments often present challenges such as long communication distances, high levels of electrical noise, and potential ground loop issues. RS-232/422 and RS-485 connections are designed to tackle these challenges effectively. RS-485, in particular, provides excellent noise immunity and allows for long communication distances of up to 1200 meters. The robustness of these serial connections ensures stable and error-free data transmission, even in demanding industrial conditions.


Cost considerations heavily influence decision-making in industrial applications. While newer technologies may offer higher data rates and advanced features, they often come with increased implementation costs. Serial connections like RS-232/422 and RS-485 provide a cost-effective solution for industrial communication needs. The low cost of serial hardware components and the abundance of supporting infrastructure, including cables and connectors, make them an economical choice for industrial deployments.

Deterministic Communication

Many industrial processes require deterministic communication, where timing and synchronization are critical. Serial connections excel in providing predictable communication with deterministic response times. The simplicity and low overhead of the serial communication protocol ensure precise control and coordination in time-sensitive applications, such as motion control systems and real-time monitoring.

Serial connections, still relevant in 2023 and beyond...

Despite the rapid advancements in communication technologies, RS-232/422 and RS-485 serial connections remain a mainstay in industrial applications. The unique advantages offered by these connections still contribute to their continued usage. The industrial sector relies on these serial connections to ensure uninterrupted data flow, seamless integration with existing infrastructure, and efficient operations. As long as these advantages persist, serial connections will continue to play a vital role in the industrial landscape, supporting a wide range of critical applications. In time, ethernet based solutions like 2-wire LAN will take over but expect serial connections to stay around for a long, long time.