RTC status register
| SEC_INT | Second interrupt flag |
| CTRL_SYNC | Control Register synchronization busy indicator |
| STATUS_SYNC | Status Register synchronization busy indicator |
| SEC_SYNC | Second configuration Register synchronization busy indicator |
| CALIB_SYNC | Calibration Register synchronization busy indicator |
| FREE_SYNC | Free running counter control Register synchronization busy indicator |
| THR_INT_SYNC | Free running counter interrupt Threshold Register synchronization busy indicator |
| THR_RST_SYNC | Free running counter Reset Threshold Register synchronization busy indicator |
| FREE_RUNNING_INT | Free running interrupt status. |