ST STM32WL55JC Reference Manual page 120

Embedded Flash memory (FLASH)
Note: Full mass erase or partial mass erase is performed only when level 1 is active and level 0 is
requested. When the protection level is increased (0→1, 1→2, 0→2, or directly decreased
from level 2 to level 0), there is no mass erase.
To validate the protection level change, the option bytes must be reloaded through the
OBL_LAUNCH bit in FLASH_CR, or a POR, or wakeup from Standby or Shutdown mode.
Write options including
RDP ≠ 0xCC and RDP ≠ 0xAA
RDP = 0xCC
Others options modified
Options write (RDP level increase) includes:
- Options page erase
- New options program
Options write (RDP level decrease) includes:
- Full mass erase or partial mass erase to not erase secure and or PCROP pages
- Backup registers and SRAM2 erase
- Options page erase
- New options program
Table 20. Access status versus protection level and execution modes
Protection
Area
level
1
Main Flash
memory
2
1
System
(2)
memory
2
1
Option bytes
2
1
Backup
registers
2
1
SRAM2
2
120/1454
Figure 8. Changing the RDP level
RDP ≠ 0xAA and RDP ≠ 0xCC
Others options modified
Write options including
RDP = 0xCC
Write options including
Level 2
RDP = 0xCC
Write options including
User execution (BootFromFlash)
Read Write
Yes Yes
Yes Yes
Yes No
Yes No
Yes Yes
CPU1 and CPU2
none secure - No
Yes
CPU2 secure - Yes CPU2 secure - Yes
Yes Yes
Yes Yes
Yes Yes
Yes Yes
Write options including
Level 1
RDP ≠ 0xAA
RDP ≠ 0xCC
default
Write options including
RDP ≠ 0xCC and RDP ≠ 0xAA
RDP = 0xCC
RDP = 0xAA
Options write (RDP level identical) includes:
Secure CPU2 options write (RDP level identical) includes:
Secure CPU2 options write (RDP level decrease) includes:
Erase
Yes
Yes
No
No
(3)
Yes
CPU1 and CPU2
none secure - No
N/A
N/A
N/A
N/A
RM0453 Rev 2
RDP = 0xAA
Level 0
RDP = 0xAA
RDP = 0xAA
Other(s) option(s) modified
- Options page erase
- New options program
- Options page erase
- New options program
- Options page erase
- New options program
Debug/ BootFromRam/
BootFromLoader/|BootFromSFI
/RSS
Read Write
No No
(1)
N/A N/A
Yes No
(1)
N/A N/A
Yes Yes
(1)
N/A N/A
No No
(1)
N/A N/A
No No
(1)
N/A N/A
RM0453
MSv62613V1
Erase
(4)
No
(1) (1)
N/A
No
(1) (1)
N/A
(3)
Yes
(1) (1)
N/A
(4)
No
(1) (1)
N/A
(5)
No
(1) (1)
N/A