Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32f4/STM32F401/PWR/CSR#0x0
power control/status register
Wakeup flag
Standby flag
PVD output
Backup regulator ready
Enable WKUP pin
Backup regulator enable
Regulator voltage scaling output selection ready bit
https://github.com/modm-io/cmsis-svd-stm32