S7-300 在启动时会将 MMC 卡中的程序加载到工作存储器中。利用这一特性，让 PLC 在复位过程中检测不到有效程序或触发复位请求，即可清除卡内数据和密码。

The STOP LED will flash rapidly while the memory is cleared. Once it stays solid again, the PLC is at factory defaults.

Prevents anyone from even viewing the blocks.

Save, compile, and download the hardware configuration to the PLC. 2. Siemens PG (Programming Device) & MMC Card

Insert a clean or secondary MMC directly into an authorized Siemens programming device.

If you do not have a backup of the PLC project, you cannot clear the hardware without permanently losing your data. You can extract the password directly from the Micro Memory Card (MMC) using low-level hex analysis. Required Tools

Open Simatic Manager or TIA Portal and generate a completely empty project file.

：使用西门子原厂传输存储卡（如 6ES7954-8LC02-0AA0、6ES7954-8LF02-0AA0 等型号），插入 CPU 后可以删除受密码保护的程序。

The S7300 PLC series is part of Siemens' SIMATIC line, designed to automate tasks in industrial settings. Its programming and configuration are typically done using STEP 7, a software tool provided by Siemens. To protect the intellectual property of the programs and configurations, as well as to prevent unauthorized changes, Siemens implemented password protection.