Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/STMicroelectronics/STM32F303/PWR/CR#0x0
power control register
Low-power deep sleep
Power down deepsleep
Clear wakeup flag
Clear standby flag
Power voltage detector enable
PVD level selection
Disable backup domain write protection
https://github.com/cmsis-svd/cmsis-svd-data