Frequency converters are widely used in various industries, but their simple display panels and weaknesses in data processing, calculation, and storage have limited their application in complex control systems. Especially in applications with multiple frequency converters under unified control, the laying of control cables increases costs and failure rates. However, combining communication technology with frequency converters can overcome these shortcomings. Remote control can be achieved using the communication function between a PLC and the frequency converter, while also enhancing the frequency converter's data processing and fault alarm functions. In the field of automation control, with the development of distributed control systems, serial communication is a simpler way to achieve remote information exchange in industrial distributed control systems. The developed RS485 is a balanced transmission electrical standard with significant improvements in electrical specifications. Due to its excellent performance, simple structure, easy networking, and low networking cost, the RS485 bus standard has been increasingly widely used. Furthermore, the MODBUS protocol used in the RS485 bus is an open communication protocol supported by many industrial control product manufacturers. This protocol has been widely applied in international standards for equipment and systems in industries such as water conservancy, hydrology, and power. This article uses the communication between a Siemens PLC and an ABB frequency converter as an example to illustrate the method of implementing communication control using the MODBUS protocol. [b]System Configuration Scheme and Communication Protocol 1. System Configuration Scheme[/b] In this system scheme, considering the application cost and practicality of the system, the PLC used is the Siemens SIMATIC S226 series. The S7-200 series is a small programmable logic controller (PLC) that can be used in simple control applications replacing relays, as well as in complex automated control systems. [b][align=center]For details, please click: Using MODBUS to Implement Communication Control between Siemens PLC and ABB Frequency Converter[/align][/b]