In the application of CC-Link fieldbus, the most critical aspect is the communication initialization setup. Currently, there are three main methods for initializing CC-Link communication. This paper compares and analyzes these three different approaches to determine which one is the simplest and most effective under various conditions. Understanding these methods holds significant practical value for engineers working with CC-Link in real-world applications. It helps reduce design workload, save time, and explore further development potential of CC-Link technology.
To facilitate the comparison of communication initialization settings, we established a small-scale CC-Link fieldbus system in the laboratory. The overall configuration is illustrated in Figure 1. Once the hardware connections are correctly set up, the communication initialization can begin.
There are three primary methods used for setting up communication parameters:
The first method involves programming to set the communication initialization parameters. As shown in Figure 2, this process includes writing key parameters such as the number of connected modules, retry count, automatic return modules, and operation specifications into the corresponding memory addresses. After executing a refresh command, these buffer memory parameters are sent to the internal registration area, initiating the data link. If the data link starts successfully, the parameters can be registered to the E2PROM using a register command. This ensures that the settings remain even after power loss. However, if the parameters are incorrect—such as mismatching with the hardware or the settings on the devices—the data link may fail without clear error messages, requiring manual checks. On the other hand, if the hardware settings are wrong, the CC-Link control component usually provides an error message, making it easier to identify and fix issues.
The second method uses GX-Configurator software to configure CC-Link communication. This tool allows users to configure PLCs from the A series and QnA series to set communication parameters easily. The configuration process is straightforward: select the master station model, add slave stations one by one, and define their models and station numbers. The final configuration is displayed clearly on the screen, making the system setup easy to understand. However, after completing the configuration, the data link might not start properly. When downloading the master parameter file, the user is asked whether to write the parameters to the E2PROM or buffer memory. Even if either option is selected, the system prompts whether to execute the data link. While the LED indicators may show normal operation, after a PLC reset, errors may occur at each station. This suggests that the configuration software does not actually write the parameters to the E2PROM. Therefore, a separate program must be used to register the parameters to the E2PROM, which adds some inconvenience but also simplifies the process of writing parameters to the buffer storage.
The third method involves setting communication parameters through network parameters on the CC-Link. This feature is available only on the small Q series PLCs, not on the A series or QnA series. During the experiment, the master module was replaced with a Q series PLC. The setup process is very convenient: by entering the correct network parameters in the GPPW software, remote I/O signals can be automatically refreshed into the CPU memory, and the initial parameters for CC-Link remote components are set automatically. This method eliminates the need for complex programming and significantly reduces setup time.
After testing all three methods, it becomes clear that each has its own advantages and disadvantages. The traditional ladder logic programming method is the most complex and time-consuming, but it offers deep insight into how the system works. The configuration software is simple and intuitive, making it ideal for quick setup, but it lacks the ability to store settings in E2PROM. The network parameter method is efficient and user-friendly, but it skips many details, making it harder to fully understand the internal workings of the PLC.
In summary, each method suits different needs and situations. For those who want to deeply understand the PLC's operation, the programming method is best. For designers looking to save time and effort, the network parameter method is more suitable. The configuration software offers a middle ground, combining ease of use with flexibility. In practice, the network parameter method for initializing communication settings is considered one of the most effective, offering convenience, reliability, and comprehensive functionality. Although it currently supports only the small Q series PLCs, future developments in communication and control technologies are expected to bring even better solutions for fieldbus applications.
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