ST STM32L4x6

Embedded Flash memory (FLASH) RM0351
102/1693 DocID024597 Rev 3
Figure 4. Changing the Read protection (RDP) level
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Table 12. Access status versus protection level and execution modes
Area
Protection
level
User execution (BootFromFlash)
Debug/ BootFromRam/
BootFromLoader
Read Write Erase Read Write Erase
Flash main
memory
1 Yes Yes Yes N o No No
(3)
2 Yes Yes Yes N/A
(1)
N/A
(1)
N/A
(1)
System
memory
(2)
1 Yes No No Yes No No
2 Yes No No NA
(1)
N/A
(1)
N/A
(1)
Option bytes
1Yes Yes
(3)
Yes Yes Yes
(3)
Yes
2 Yes No No N/A
(1)
N/A
(1)
N/A
(1)
Backup
registers
1 Yes Yes N/A No No No
(4)
2Yes YesN/A N/A
(1)
N/A
(1)
N/A
(1)
SRAM2
1 Yes Yes N/A No No No
(5)
2Yes YesN/A N/A
(1)
N/A
(1)
N/A
(1)
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.