Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32h7/STM32H745_CM4/SYSCFG/UR1#0x0
SYSCFG user register 1
Boot Cortex-M4
Boot Cortex-M7
https://github.com/modm-io/cmsis-svd-stm32