22.1 Description

The Real-time Clock (RTC) is designed for very low power consumption. The RTC requires an accurate external 32.768 kHz clock, which can be provided by a crystal oscillator.

The RTC combines a complete time-of-day clock with alarm and a Gregorian or Persian calendar or UTC mode, complemented by a programmable periodic interrupt. The alarm and calendar registers are accessed by a 32-bit data bus.

In Gregorian mode, 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 can compensate for crystal oscillator frequency variations.

Two RTC outputs can be programmed to generate several waveforms, including a prescaled clock derived from 32.768 kHz.

Timestamping capability reports the first and last occurrences for each tamper event detected on TMPx pins.