RM0444 Rev 5 93/1390
RM0444 Embedded Flash memory (FLASH)
118
Once in Level 2, it is no more possible to modify the read protection level.
With the PCROP_RDP bit of the FLASH PCROP area A end address register
(FLASH_PCROP1AER) set, the change from Level 1 to Level 0 triggers full mass erase of
the Main Flash memory. The backup registers (TAMP_BKPxR) are also erased. The user
options except PCROP protection are set to their previous values copied from
FLASH_OPTR and FLASH_WRPyxR (x = A or B, y = 1 or 2). PCROP is disabled. The OTP
area is not affected by mass erase and remains unchanged.
With the PCROP_RDP bit cleared, a partial mass erase occurs, only erasing Flash memory
pages that do not overlap with PCROP area (do not contain any PCROP-protected
subpage). The option bytes are re-programmed with their previous values. This is also true
for FLASH_PCROP1xSR and FLASH_PCROP1xER registers (x = A or B).
Note: Mass erase (full or partial) is only triggered by the RDP regression from Level 1 to Level 0.
RDP level increase (Level 0 to Level 1, 1 to 2, or 0 to 2) does not cause any mass erase.
To validate the protection level change, the option bytes must be reloaded by setting the
OBL_LAUNCH bit of the FLASH control register (FLASH_CR).
Table 18: Mass erase upon RDP regression from Level 1 to Level 0
PCROP
area
PCROP_RDP Mass erase
None x
Full
(Flash memory and backup register)
Part of
Flash
memory
1
0
Partial
(Flash memory pages not overlapping with PCROP area, and backup
registers)
Full Flash
memory
None
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