RM0453 Rev 5 123/1450
RM0453 Embedded flash memory (FLASH)
154
Note: It is recommended to align PCROP areas with the page granularity when using
PCROP_RDP, or to leave free the rest of the page where PCROP zones starts or ends.
4.6.3 Write protection (WRP)
The user area in the flash memory can be protected against unwanted write operations. Two
write-protected (WRP) areas can be defined, with 2-Kbyte granularity page. Each area is
defined by a start page offset and an end page offset related to the physical flash memory
base address. These offsets are defined in the WRP address registers FLASH_WRP1AR
and FLASH_WRP1BR.
The WRP “x” area (x = A, B) is defined from the address:
Flash memory Base address + [WRP1x_STRT x 0x800] (included) to the address:
Flash memory Base address + [(WRP1x_END+1) x 0x800] (excluded).
The minimum WRP area size is one WRP 2_Kbyte page, WRP1x_END = WRP1x_STRT.
For example, to protect by WRP from the address 0x0801 2000 (included) to the address
0x0801 9FFF (included), if boot in flash is selected, FLASH_WRP1AR register must be
programmed with:
• WRP1A_STRT = 0x24
• WRP1A_END = 0x33
WRP1B_STRT and WRP1B_END in FLASH_WRP1BR can be used instead (area “B” in
flash memory).
When WRP is active, it cannot be erased or programmed. Consequently, a software mass
erase cannot be performed if one area is write-protected.
If an erase/program operation to a write-protected part of the flash memory is attempted, the
write protection error flag (WRPERR) is set in FLASH_SR. This flag is also set for any write
access to on the following area:
• OTP area
• part of the flash memory that can never be written like the ICP
• PCROP area
Note: When the flash memory readout protection level is selected (RDP level1), it is not possible
to program or erase the memory if the CPU debug features are connected (JTAG or single
wire) or boot code is being executed from RAM or system flash, even if WRP is not
activated. Any attempt generates an hard fault (BusFault).
Table 21: PCROP protection
PCROP registers values (x = A or B) PCROP protection area
PCROP1x_STRT = PCROP1x_END No PCROP1x, unprotected
PCROP1x_STRT > PCROP1x_END No PCROP1x, unprotected
PCROP1x_STRT < PCROP1x_END Pages from PCROP1x_STRT to PCROP1x_END are protected
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