Bitfields for RTC status register B:
Bit(s)	Description	)
 7	clear if normal update, set if abort update
 6	periodic interrupt enable
 5	alarm interrupt enable
 4	update end interrupt enable
 3	square wave enable
 2	date mode (clear = BCD, set = binary)
 1	24-hour format
 0	daylight saving time enable
SeeAlso: #00405