Figure 6. Pcrop Levels - ST STM32F423 Reference Manual

Embedded Flash memory interface
The deactivation of the SPRMOD and/or the unprotection of PCROPed user sectors can
only occur when, at the same time, the RDP level changes from 1 to 0. If this condition is not
respected, the user option byte modification is canceled and the write error WRPERR flag is
set. The modification of the users option bytes (BOR_LEV, RST_STDBY, ..) is allowed since
none of the active nWRPi bits is reset and SPRMOD is kept active.
Note: The active value of nWRPi bits is inverted when PCROP mode is active (SPRMOD =1).
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Figure 6. PCROP levels

RM0430 Rev 8
RM0430