Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32f4/STM32F405/FSMC/SDSR#0x0
SDRAM Status register
Refresh error flag
Status Mode for Bank 1
Status Mode for Bank 2
Busy status
https://github.com/modm-io/cmsis-svd-stm32