Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32n6/STM32N655/MCE1/MCE_CC2NR1#0x0
MCE cipher context 2 nonce register 1
Stream cipher nonce, bits [63:32]
https://github.com/modm-io/cmsis-svd-stm32