ATXMEGA8E5_14 datasheet(21/147 Pages) ATMEL

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XMEGA E5 [DATASHEET]

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

Figure 11-1. The clock system, clock sources and clock distribution.

11.3

Clock Sources

The clock sources are divided in two main groups: internal oscillators and external clock sources. Most of the clock

sources can be directly enabled and disabled from software, while others are automatically enabled or disabled,

depending on peripheral settings. After reset, the device starts up running from the 2MHz output of the 8MHz internal

oscillator. The other clock sources, DFLL and PLL, are turned off by default.

The internal oscillators do not require any external components to run. For details on characteristics and accuracy of the

internal oscillators, refer to the device datasheet.

11.3.1 32kHz Ultra Low Power Internal Oscillator

This oscillator provides an approximate 32kHz clock. The 32kHz ultra low power (ULP) internal oscillator is a very low

power clock source, and it is not designed for high accuracy. The oscillator employs a built-in prescaler that provides a

Real Time

Counter

Peripherals

RAM

AVR CPU

Non-Volatile

Memory

Watchdog

Timer

Brown-out

Detector

System Clock Prescalers

System Clock Multiplexer

(SCLKSEL)

32 kHz

Int. ULP

32.768 kHz

Int. OSC

32.768 kHz

TOSC

8MHz

Int. Osc

32 MHz

Int. Osc

0.4 – 16 MHz

XTAL

PLL

clkSYS

clkRTC

clkPER2

clkPER

clkCPU

clkPER4

XOSCSEL

RTCSRC

PLLSRC

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