
318
SAM G51 [DATASHEET]
11209C–ATARM–20-Dec-13
14.3
Block Diagram
Figure 14-1.
RTC Block Diagram
14.4
Product Dependencies
14.4.1 Power Management
The Real-time Clock is continuously clocked at 32.768 kHz. The Power Management Controller has no effect on RTC
behavior.
14.4.2 Interrupt
RTC interrupt line is connected on one of the internal sources of the interrupt controller. RTC interrupt requires the
interrupt controller to be programmed first.
14.5
Functional Description
The RTC provides a full binary-coded decimal (BCD) clock that includes century (19/20), year (with leap years), month,
date, day, hours, minutes and seconds.
The valid year range is 1900 to 2099 in Gregorian mode, a two-hundred-year calendar(or 1300 to 1499 in Persian mode).
The RTC can operate in 24-hour mode or in 12-hour mode with an AM/PM indicator.
Corrections for leap years are included (all years divisible by 4 being leap years). This is correct up to the year 2099.
The RTC can generate events to trigger ADC measurements.
14.5.1 Reference Clock
The reference clock is Slow Clock (SLCK). It can be driven internally or by an external 32.768 kHz crystal.
During low power modes of the processor, the oscillator runs and power consumption is critical. The crystal selection has
to take into account the current consumption for power saving and the frequency drift due to temperature effect on the
circuit for time accuracy.
14.5.2 Timing
The RTC is updated in real time at one-second intervals in normal mode for the counters of seconds, at one-minute
intervals for the counter of minutes and so on.
Due to the asynchronous operation of the RTC with respect to the rest of the chip, to be certain that the value read in the
RTC registers (century, year, month, date, day, hours, minutes, seconds) are valid and stable, it is necessary to read
these registers twice. If the data is the same both times, then it is valid. Therefore, a minimum of two and a maximum of
three accesses are required.
User Interface
32768 Divider
Time
Slow Clock: SLCK
APB
Date
RTC Interrupt
Entry
Control
Interrupt
Control
Clock Calibration
ADC AD[7:0]
trigger
ADC AD[7]
trigger
Wave
Generator
Alarm