Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32n6/STM32N645/RAMCFG/RAMCFG_BKPSRAMECCKEYR#0x0
RAMCFG BKPSRAM ECC key register
ECC write protection key
https://github.com/modm-io/cmsis-svd-stm32