RM0440 Rev 4 167/2126
RM0440 Embedded Flash memory (FLASH) for category 4 devices
228
If the bit PCROP_RDP is cleared in the FLASH_PCROP1ER, the full mass erase is
replaced by a partial mass erase that is successive page erases, except for the pages
protected by PCROP. This is done in order to keep the PCROP code. Only when the Flash
memory is erased, options are re-programmed with their previous values. This is also true
for FLASH_PCROPxSR and FLASH_PCROPxER registers (x=1).
Note: Full Mass Erase or Partial Mass Erase is performed only when Level 1 is active and Level 0
requested. When the protection level is increased (0->1, 1->2, 0->2) there is no mass erase.
To validate the protection level change, the option bytes must be reloaded through the
OBL_LAUNCH bit in Flash control register.
Figure 7. Changing the read protection (RDP) level
MS33468V2
Options write (RDP level increase) includes:
- Options page erase
- New options program
RDP ≠ 0xAA and RDP ≠ 0xCC
Others options modified
Write options including
RDP = 0xAA
Write options Including
RDP = 0xCC
Write options including
RDP ≠ 0xCC and RDP ≠ 0xAA
Level 1
RDP ≠ 0xAA
RDP ≠ 0xCC
default
Level 2
RDP = 0xCC
Level 0
RDP = 0xAA
RDP = 0xAA
Other(s) option(s) modified
Write options including
RDP = 0xCC
Options write (RDP level decrease) includes
- Full Mass erase or Partial Mass erase to not
erase PCROP pages if PCROP_RDP is cleared
- Backup registers and CCM SRAM erase
- Options page erase
- New options program
Options write (RDP level identical) includes
- Options page erase
- New options program
Table 23. Access status versus protection level and execution modes
Area
Protection
level
User execution (BootFromFlash)
Debug/ BootFromRam/
BootFromLoader
(1)
Read Write Erase Read Write Erase
Flash main
memory
1 Yes Yes Yes No No No
(3)
2 Yes Yes Yes N/A N/A N/A
System
memory
(2)
1 Yes No No Yes No No
2 Yes No No N/A N/A N/A
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