How to erase stm32157f-dk2 OTP word31 area ?

[jerry123]

Hello,

I have programmed the OTP word 31 to 0xBBBBBBBB as follows, but when I want to write another value such as 0x12345678 or 0x00000000 to word 31, it reported the following errors， can you help to analyze this ?

 

Thanks a lot!

 

 

[Hal3]

You are trying to change OTP One Time Programmable to TTP Two Times Programmable.

Use another address or a fresh chip.

[jerry123]

got it, thanks a lot!