Datasheet

22
XMEGA E5 [DATASHEET]
Atmel-8153J–AVR-ATxmega8E5-ATxmega16E5-ATxmega32E5_Datasheet–11/2014
11.3.2 32.768kHz Calibrated Internal Oscillator
This oscillator provides an approximate 32.768kHz clock. It is calibrated during production to provide a default frequency
close to its nominal frequency. The calibration register can also be written from software for run-time calibration of the
oscillator frequency. The oscillator employs a built-in prescaler, which provides both a 32.768kHz output and a 1.024kHz
output.
11.3.3 32.768kHz Crystal Oscillator
A 32.768kHz crystal oscillator can be connected between the TOSC1 and TOSC2 pins and enables a dedicated low
frequency oscillator input circuit. A low power mode with reduced voltage swing on TOSC2 is available. This oscillator
can be used as a clock source for the system clock and RTC, and as the DFLL reference clock.
11.3.4 0.4 - 16MHz Crystal Oscillator
This oscillator can operate in four different modes optimized for different frequency ranges, all within 0.4 - 16MHz.
11.3.5 8MHz Calibrated Internal Oscillator
The 8MHz calibrated internal oscillator is the default system clock source after reset. It is calibrated during production to
provide a default frequency close to its nominal frequency. The calibration register can also be written from software for
run-time calibration of the oscillator frequency. The oscillator employs a built-in prescaler, with 2MHz output. The default
output frequency at start-up and after reset is 2MHz. A low power mode option can be used to enable fast system wake-
up from power-save mode. In all other modes, the low power mode can be enabled to significantly reduce the power
consumption of the internal oscillator.
11.3.6 32MHz Run-time Calibrated Internal Oscillator
The 32MHz run-time calibrated internal oscillator is a high-frequency oscillator. It is calibrated during production to
provide a default frequency close to its nominal frequency. A digital frequency looked loop (DFLL) can be enabled for
automatic run-time calibration of the oscillator to compensate for temperature and voltage drift and optimize the oscillator
accuracy. This oscillator can also be adjusted and calibrated to any frequency between 30 and 55MHz.
11.3.7 External Clock Sources
The XTAL1 and XTAL2 pins can be used to drive an external oscillator, either a quartz crystal or a ceramic resonator.
XTAL1 or pin 4 of port C (PC4) can be used as input for an external clock signal. The TOSC1 and TOSC2 pins are
dedicated to driving a 32.768kHz crystal oscillator.
11.3.8 PLL with 1x-31x Multiplication Factor
The built-in phase locked loop (PLL) can be used to generate a high-frequency system clock. The PLL has a user-
selectable multiplication factor of from 1 to 31. In combination with the prescalers, this gives a wide range of output
frequencies from all clock sources.