First of all, let's clarify something: In the configuration of certain blocks in the original PLC, is the serial number of the associated CPU set in the "Copy Protection" section? If it is, then the original SMC card cannot be directly used in a new CPU. In such cases, the source program must be removed or reconfigured to match the new hardware. The S-1500 uses the SIMATIC memory card (SMC). No matter which download method you use, the program must first be downloaded to the SMC and then transferred to the PLC. The SMC serves as a storage medium for code blocks (such as OBs, FBs, and FCs), data blocks, technology objects, hardware configurations, variable symbols, comments, and data types—information that is not stored in the PLC's working memory. When the SMC card is inserted, the CPU compares the configuration stored on the SIMATIC memory card with the retentive backup data. With a new CPU, there will inevitably be differences in the data, which causes 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) are loaded into the CPU’s working memory. As long as the order number and version number of the CPU match, the PLC should function properly without any issues. It's important to note that when replacing a CPU, always check the copy protection settings first. If enabled, you may need to reprogram or relicense the system. This step can save time and prevent unexpected errors during the installation process. Additionally, make sure to back up all critical data before making any hardware changes. This ensures that you can restore the system quickly in case something goes wrong. Back-Up UPS,Avr Boost And Buck,Battery Low Voltage Protection,Dual Voltage Power Supply Shenzhen Unitronic Power System Co., Ltd , https://www.unitronicpower.com