ATXMEGA8E5_14 datasheet(40/147 Pages) ATMEL

40 / 147 page

XMEGA E5 [DATASHEET]

Atmel-8153I–AVR-ATxmega8E5-ATxmega16E5-ATxmega32E5_Datasheet–08/2014

21.

RTC – 16-bit Real-Time Counter

21.1

Features

16-bit resolution

Selectable clock source

32.768kHz external crystal

External clock

32.768kHz internal oscillator

32kHz internal ULP oscillator

Programmable 10-bit clock prescaling

One compare register

One period register

Clear counter on period overflow

Optional interrupt/event on overflow and compare match

Correction for external crystal oscillator frequency error down to ±0.5 ppm accuracy

21.2

Overview

The 16-bit real-time counter (RTC) is a counter that typically runs continuously, including in low power sleep modes, to

keep track of time. It can wake up the device from sleep modes and/or interrupt the device at regular intervals.

The reference clock is typically the 1.024kHz output from a high-accuracy crystal of 32.768kHz, and this is the

configuration most optimized for low power consumption. The faster 32.768kHz output can be selected if the RTC needs

a resolution higher than 1ms. The RTC can also be clocked from an external clock signal, the 32.768kHz internal

oscillator or the 32kHz internal ULP oscillator.

The RTC includes a 10-bit programmable prescaler that can scale down the reference clock before it reaches the

counter. A wide range of resolutions and time-out periods can be configured. With a 32.768kHz clock source, the

maximum resolution is 30.5μs, and time-out periods can range up to 2000 seconds. With a resolution of 1s, the

maximum timeout period is more than 18 hours (65536 seconds). The RTC can give a compare interrupt and/or event

when the counter equals the compare register value, and an overflow interrupt and/or event when it equals the period

ATXMEGA8E5 датащи(PDF) 40 Page - ATMEL Corporation