Table 12. Access Status Versus Protection Level And Execution Modes; Figure 4. Changing The Read Protection (Rdp) Level - ST STM32L4x6 Reference Manual

Embedded Flash memory (FLASH)

Table 12. 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
1
Backup
registers
2
1
SRAM2
2
1. When the protection level 2 is active, the Debug port, the boot from RAM and the boot from system memory are disabled.
2. The system memory is only read-accessible, whatever the protection level (0, 1 or 2) and execution mode.
3. The Flash main memory is erased when the RDP option byte is programmed with all level protections disabled (0xAA).
4. The backup registers are erased when RDP changes from level 1 to level 0.
5. The SRAM2 is erased when RDP changes from level 1 to level 0.
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Figure 4. Changing the Read protection (RDP) level

User execution (BootFromFlash)
Read Write
Yes Yes
Yes Yes
Yes No
Yes No
(3)
Yes Yes
Yes No
Yes Yes
Yes Yes
Yes Yes
Yes Yes
DocID024597 Rev 3
Debug/ BootFromRam/
BootFromLoader
Erase Read
Yes No
(1)
Yes N/A
No Yes
(1)
No NA
Yes Yes
(1)
No N/A
N/A No
(1)
N/A N/A
N/A No
(1)
N/A N/A
RM0351
Write Erase
(3)
No No
(1) (1)
N/A N/A
No No
(1) (1)
N/A N/A
(3)
Yes Yes
(1) (1)
N/A N/A
(4)
No No
(1) (1)
N/A N/A
(5)
No No
(1) (1)
N/A N/A