Write Protections; Figure 5. Rdp Levels - ST STM32F446 Series Reference Manual

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Figure 5
3.6.4

Write protections

Up to 7 user sectors in Flash memory can be protected against unwanted write operations
due to loss of program counter contexts. When the non-write protection nWRPi bit (0 ≤ i ≤ 7)
in the FLASH_OPTCR or FLASH_OPTCR1 registers is low, the corresponding sector
cannot be erased or programmed. Consequently, a mass erase cannot be performed if one
of the sectors is write-protected.
If an erase/program operation to a write-protected part of the Flash memory is attempted
(sector protected by write protection bit, OTP part locked or part of the Flash memory that
can never be written like the ICP), the write protection error flag (WRPERR) is set in the
FLASH_SR register.
Note: When the memory read protection level is selected (RDP level = 1), it is not possible to
program or erase Flash memory sector i if the CPU debug features are connected (JTAG or
single wire) or boot code is being executed from RAM, even if nWRPi = 1.
Write protection error flag
If an erase/program operation to a write protected area of the Flash memory is performed,
the Write Protection Error flag (WRPERR) is set in the FLASH_SR register.
shows how to go from one RDP level to another.
Embedded Flash memory interface

Figure 5. RDP levels

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