The secondary protection of the chip will appear as follows:
The chip cannot be connected to the chip via st-link after using secondary protection.
If you use secondary protection, you should be able to solve secondary protection (which needs to be confirmed) if you use an official ISP.
However, if the 1boot_bit in OPTION OPTION is set to 1,BOOT0 and also set to 1, then the startup is Embedded SRAM mode.
In this case, how to remove the secondary protection of the chip? Or just scrap the chip?
So far I'm, I'm on the development board, and the test results are
1. STVP cannot connect to the development board
2. The official ISP cannot find chips through UART (because at this time,Embedded SRAM startup mode)