SLAU847D October 2022 – May 2024 MSPM0L1105 , MSPM0L1106 , MSPM0L1227 , MSPM0L1228 , MSPM0L1228-Q1 , MSPM0L1303 , MSPM0L1304 , MSPM0L1304-Q1 , MSPM0L1305 , MSPM0L1305-Q1 , MSPM0L1306 , MSPM0L1306-Q1 , MSPM0L1343 , MSPM0L1344 , MSPM0L1345 , MSPM0L1346 , MSPM0L2227 , MSPM0L2228 , MSPM0L2228-Q1
The static write protection scheme is configured and latched during device boot by the immutable ROM boot code before the main application in flash can execute. After a flash sector is configured to be write protected through the static write protection mechanism, software cannot remove the protection at runtime without a reboot. Thus, sectors protected by static write protection can be thought of as immutable after boot. This type of protection is useful for protecting a custom bootloader in a dual-image application, or for extending the secure root of trust from the ROM boot code into a portion of the main flash region to enable a secure boot manager with locked public keys.
The static write protection scheme is configured by programming the appropriate bits in the NONMAIN flash region, which is read by the boot code before the main application starts. The NONMAIN flash sector can be statically write protected, resulting in a system in which the static write protection scheme is fully permanent and cannot be modified. If the NONMAIN sector is configured to be statically protected, along with any other flash sectors, all statically protected flash sectors can be functionally viewed as read only memory which cannot be updated by any means.
Static write protection can be configured for all sectors of flash memory across all banks present on a device. Instructions for configuring the static write protection, along with the rest of the NONMAIN region, are given in Section 1.4.