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STM32L151VE optionbytes "nBFB2" bit question


Hi sir,

I ask a question about optionbytes nBFB2 of STM32L151VE.

I checked User Manual and wanted to confirm some information about nBFB2.

1) Option byte register (FLASH_OBR) : bit nBFB2 default value = 1 , see attached file optionbytes_1.png

2) Option byte memory address 0x1FF8 0004H : read bit7 = BFB2 value, but there is no default value describtion about this bit.

My question:

1) Which default value is nBFB2 ? 0 or 1 ?

2) If user read address 0x1FF8 0004H to get bit7(nBFB2) = 0, then try to write 1 using FLASH_OB_BORConfig(), MCU should does a reset behavior , right?

After MCU reset, then read this address again, user should get bit7(nBFB2) = 1, then code execute users app code.

Is my understanding right or not? If right, where i could get this information description on ST spec? Would you mind give me the link?

Thanks a lot and hope your help ASAP.

Best Regards,


Associate II

I'm having the same issue.STM32L151RET6,nBFB2,default value maybe is 1, but some is 0, so the mcu reset and rest.