RV-4162 Datasheet, PDF (22/39 Pages) MICORO CRYSTAL SWITZERLAND – Ultra Small Real Time Clock

Micro Crystal
Ultra Small Real Time Clock / Calendar Module
RV-4162
4.5. CENTURY BITS
The two century bits, CB1 and CB0, are bits 7 and 6, respectively, in the Month / Century register at address 06h.
Together, they comprise a 2-bit counter which increments at the turn of each century. CB1 is the most significant
bit.
The user may arbitrarily assign the meaning of CB1:CB0 to represent any century value, but the simplest way of
using these bits is to extend the Years register (07h) by mapping them directly to bits 9 and 8 (the reader is
reminded that the year register is in BCD format). Higher order year bits can be maintained in the application
software.
Century bits CB1 and CB0:
4.6. LEAP YEAR
Leap year occurs every four years, in years which are multiples of 4. For example, 2012 was a leap year. An
exception to that is any year which is a multiple of 100. For example, the year 2100 is not a leap year. A further
exception is that years which are multiples of 400 are indeed leap years. Hence, while 2100 is not a leap year,
2400 is.
During any year which is a multiple of 4, the RV-4162 RTC will automatically insert leap day, February 29.
Therefore, the application software must correct for this during the exception years (2100, 2200, etc.) as noted
above.
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