FLASH option status register
| BOR_LEV | BOR reset level option configuration bits |
| IWDG1_SW | IWDG1 option configuration bit |
| NRST_STOP_D1 | Option byte erase after D1 DStop option configuration bit |
| NRST_STBY_D1 | Option byte erase after D1 DStandby option configuration bit |
| RDP | Readout protection level option configuration byte |
| IWDG_FZ_STOP | IWDG Stop mode freeze option configuration bit |
| IWDG_FZ_SDBY | IWDG Standby mode freeze option configuration bit |
| ST_RAM_SIZE | DTCM size select option configuration bits |
| SECURITY | Security option configuration bit |
| IO_HSLV | I/O high-speed at low-voltage (PRODUCT_BELOW_25V) |