285
SAM4CP [DATASHEET]
43051E–ATPL–08/14
17.
Real-time Clock (RTC)
17.1
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
17.2
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
Tamper TimeStamping Registers
Register Write Protection
17.3
Block Diagram
Figure 17-1.
RTC Block Diagram
User Interface
32768 Divider
Time
Slow Clock: SLCK
APB
Date
RTC Interrupt
Entry
Control
Interrupt
Control
Clock Calibration
RTCOUT0
Wave
Generator
Alarm