RTC Counter

The RTC counter keeps track of seconds, minutes, hours, days, weeks, and years when in Calendar mode, and for this purpose it requires a 43-bit counter. When counting in Binary mode, the 43-bit register is treated as a linear up counter.

The following table lists the detail for Calendar mode and Binary mode.

Table 1. Calendar Counter Description
Function	Number of Bits	Range		Reset Value
Function	Number of Bits	Calendar Mode	Binary Mode	Calendar Mode	Binary Mode
Second	6	0-59	0-63	0	0
Minute	6	0-59	0-63	0	0
Hour	5	0-23	0-31	0	0
Day	5	1-31 (auto adjust by month and year)	0-31	1	0
Month	4	1-12	0-15	1	0
Year	8	0-255 Year 2000 to 2255	0-255	0 (year 2000)	0
Weekday	3	1-7	0-7	7	0
Week	6	1-52	0-63	1	0

Note: The long-term accuracy of the RTC depends on the accuracy of the external reference frequency. For instance, if the external reference frequency is 124.988277868 MHz rather than 125 MHz, the RTC loses approximately 7.4 seconds over 24 hours.