Method for repairing on-site PLC damage

If it is indeed protected and the CPU serial number is bound, then the original SMC card cannot be directly used in a new CPU. In this case, you will need to remove the source program before proceeding.

The S-1500 system uses the SIMATIC Memory Card (SMC). No matter which download method you choose, the program must first be downloaded to the SMC and then transferred to the PLC. The SMC serves as a storage medium for various elements such as code blocks (like OB, FB, FC), data blocks, technology objects, hardware configurations, variable symbols, comments, and data types—none of which are stored in the PLC’s working memory.

When the SMC is inserted into the CPU, the system compares the configuration on the SIMATIC memory card with the retentive backup data. With a new CPU, there will likely be differences in the data, causing the CPU to automatically reset the memory and enter STOP mode.

Therefore, if there is no copy protection in place, the contents of the load memory (i.e., the SMC card) will be loaded into the CPU’s working memory. As long as the order number and version number of the CPU match, the PLC should function normally without any issues.

It's important to note that when replacing a CPU, especially in an industrial automation environment, always verify the settings and configurations beforehand. This helps avoid unexpected errors or downtime. If you're unsure about the copy protection status, it's best to check with the manufacturer or consult the documentation for your specific PLC model. Additionally, keeping a backup of your SMC card is always a good practice to ensure smooth transitions and quick recovery in case of failures.