If you do not need the program inside the PLC and only want to reuse the hardware, you can reset the PLC to factory defaults. This will erase the program, the password, and all data on the MMC. (Memory Reset) and hold it down. The STOP LED will light up.
. Using standard consumer MMCs or formatting the card in Windows will render it unusable for the PLC. Do you have a backup of the project on your laptop, or do you need to extract the code from the PLC? S7 300 PLC password | PLCtalk - Interactive Q & A
Unlocking a Siemens SIMATIC S7-300 PLC password typically involves either using a default factory password for older units or performing a full memory reset, which deletes the current program. 1. Try Default Passwords unlock s7300 plc password
Turn the CPU switch to (Memory Reset) and hold it there. The LED will light up; keep holding until the LED flashes. Release the switch and immediately turn it to MRES again.
Open the exported source file using a standard text editor like Notepad. If you do not need the program inside
Siemens PG (Programming Device) or the official USB Prommer (order number 6ES7792-0AA00-0XA0 ) can format or delete data on an MMC card. This is the vendor‑recommended approach when all else fails, though it will erase all programmes and data.
Allows monitoring, but requires a password to edit or download new code. The STOP LED will light up
position and hold it until the STOP LED lights up and stays on (about 3 seconds). Release and Repeat:
