Abstract : This paper briefly introduces a method for acquiring time data through communication between a PLC and a frequency converter using the macro function of the OMRON programmable logic controller (PLC) communication protocol. Keywords : PLC; frequency converter; communication protocol macro. With the rapid development of microcomputer control technology and electrical drive technology in industrial control, AC variable frequency speed regulation technology is increasingly becoming one of the mainstream technologies in industrial control. The combination of programmable logic controllers and AC variable frequency technology has played a significant role in the transformation of traditional industrial equipment. In the roller hearth furnace production line, the main drive parts of the original quenching furnace and tempering furnace now use a combination of PLC and frequency converter to control the drive motor, ensuring the accuracy and reliability of the drive speed regulation. Based on the characteristics and technical requirements of this system, the OMRON C200HG CPU was selected, and the frequency converter used is the Emerson TD1000-41D015G. Here, the PLC needs to communicate with two frequency converters: one controls the main drive motor of the quenching furnace, and the other controls the main drive motor of the tempering furnace. The PLC and frequency converters communicate via serial communication using the widely applicable RS-485 interface. This part is shown in Figure 1. [b][align=center]For more details, please click: Application of PLC Communication with Multiple Frequency Converters[/align][/b]