ST STM32L4+ Series Reference Manual page 145

RM0432
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.
Write options Including
Options write (RDP level increase) includes:
Options write (RDP level decrease) includes
Table 16. Access status versus protection level and execution modes
Protection
Area
level
1
Flash main
memory
2
1
System
(2)
memory
2
1
Option bytes
2
Figure 6. Changing the Read protection (RDP) level
RDP = 0xCC
Level 2
RDP = 0xCC
- Options page erase
- New options program
- Full Mass erase or Partial Mass erase to not
erase PCROP pages if PCROP_RDP is cleared
- Backup registers and SRAM2 erase
- Options page erase
- New options program
User execution (BootFromFlash)
Read Write
Yes
Yes
Yes
Yes
Yes Yes
Yes
RDP ≠ 0xAA and RDP ≠ 0xCC
Others options modified
Level 1
RDP ≠ 0xAA
RDP ≠ 0xCC
default
Write options including
RDP ≠ 0xCC and RDP ≠ 0xAA
Write options including
RDP = 0xCC
Erase
Yes Yes
Yes Yes
No No
No No
(3)
Yes
No No
RM0432 Rev 6
Embedded Flash memory (FLASH)
Write options including
RDP = 0xAA
Level 0
RDP = 0xAA
RDP = 0xAA
Other(s) option(s) modified
Options write (RDP level identical) includes
- Options page erase
- New options program
Debug/ BootFromRam/
BootFromLoader
Read Write
No No
N/A N/A
Yes No
N/A N/A
(3)
Yes Yes
N/A N/A
MSv61195V1
(1)
Erase
(3)
No
N/A
No
N/A
Yes
N/A
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