Siemens Mmc Card Format Tool __link__ -

If you cannot communicate with the PLC via software, you can perform a manual reset using the mode switch on the CPU. Ensure the MMC is slotted into the CPU. Hold the selector switch in the position for approximately until the STOP LED lights up continuously.

An MMC is not just a storage device; it's the boot device. When you format a card, it is empty. If you plug an empty card into an S7-300 CPU, the CPU has no hardware configuration. It will likely go into STOP mode or report a configuration mismatch. siemens mmc card format tool

The Siemens MMC Card Format Tool is a powerful last resort. Do not use it casually. If you cannot communicate with the PLC via