If you are locked out of the PLC hardware itself (cannot upload/download), there are a few documented methods:
The second barrier is when the physical PLC unit is password-protected to prevent unauthorized uploads or changes. There are essentially two scenarios here: knowing the password and simply forgetting it, or not knowing it at all. The only official method to clear a forgotten CPU password is to , which erases both the password and the program inside. This can be done using a Siemens PG or an official USB programmer (6ES7792-0AA00-0XA0). unlock s7300exe work
If rescuing the existing code is not a priority and you simply want to repurpose the physical hardware, you can completely wipe the hardware lock manually. Memory Reset (MRES) Toggle Sequence S7-300 MMC Password Recovery Guide | PDF - Scribd If you are locked out of the PLC
Locate the physical mode selector toggle switch on the front panel and turn it to . This can be done using a Siemens PG
This tool recovers the CPU password for uploads/downloads; it may not unlock individual Function Blocks (FBs) protected by Know-How Protect .