Datasheet

286
SAM4S Series [DATASHEET]
11100F–ATARM–29-Jan-14
16. Real-time Clock (RTC)
16.1 Description
The Real-time Clock (RTC) peripheral is designed for very low power consumption. For optimal functionality, the RTC
requires an accurate external 32.768 kHz clock, which can be provided by a crystal oscillator.
It combines a complete time-of-day clock with alarm and a two-hundred-year Gregorian or Persian calendar,
complemented by a programmable periodic interrupt. The alarm and calendar registers are accessed by a 32-bit data
bus.
The time and calendar values are coded in binary-coded decimal (BCD) format. The time format can be 24-hour mode or
12-hour mode with an AM/PM indicator.
Updating time and calendar fields and configuring the alarm fields are performed by a parallel capture on the 32-bit data
bus. An entry control is performed to avoid loading registers with incompatible BCD format data or with an incompatible
date according to the current month/year/century.
A clock divider calibration circuitry enables to compensate crystal oscillator frequency inaccuracy.
An RTC output can be programmed to generate several waveforms, including a prescaled clock derived from 32.768
kHz.
16.2 Embedded Characteristics
 Ultra Low Power Consumption
 Full Asynchronous Design
 Gregorian Calendar up to 2099 or Persian Calendar
 Programmable Periodic Interrupt
 Safety/security features:
 Valid Time and Date Programmation Check
 On-The-Fly Time and Date Validity Check
 Crystal Oscillator Clock Calibration
 Waveform Generation
 Register Write Protection