RTC alarm B register
| SU | Second units in BCD format |
| ST | Second tens in BCD format |
| MSK1 | Alarm B seconds mask |
| MNU | Minute units in BCD format |
| MNT | Minute tens in BCD format |
| MSK2 | Alarm B minutes mask |
| HU | Hour units in BCD format |
| HT | Hour tens in BCD format |
| PM | AM/PM notation |
| MSK3 | Alarm B hours mask |
| DU | Date units or day in BCD format |
| DT | Date tens in BCD format |
| WDSEL | Week day selection |
| MSK4 | Alarm B date mask |