ATXMEGA256A3U Datasheet, PDF (20/116 Pages) ATMEL Corporation – 8/16-bit Atmel XMEGA A3U Microcontroller

XMEGA A3U
10.3.3
10.3.4
10.3.5
10.3.6
10.3.7
10.3.8
32.768kHz Crystal Oscillator
A 32.768kHz crystal oscillator can be connected between TOSC1 and TOSC2 pins and enable 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 clock source for the System Clock, RTC
and as the DFLL reference clock.
0.4 - 16MHz Crystal Oscillator
The 0.4 - 16MHz Crystal Oscillator is a driver intended for driving both external resonators and
crystals ranging from 400kHz to 16MHz.
2MHz Run-time Calibrated Internal Oscillator
The 2MHz Run-time Calibrated Internal Oscillator is the default system clock source after reset.
It is calibrated during production to provide a default frequency which is close to its nominal fre-
quency. A Digital Frequency Looked Loop (DFLL) that can be enabled for automatic run-time
calibration of the oscillator to compensate for temperature and voltage drift to optimize the oscil-
lator accuracy.
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 which is close to its nominal frequency. A DFLL
that can be enabled for automatic run-time calibration of the oscillator to compensate for temper-
ature and voltage drift to optimize the oscillator accuracy This oscillator can also be adjusted
and calibrated to any frequency between 30 and 55MHz.
External Clock input
The external clock input gives the possibility to connect a clock from an external source to
XTAL1.
PLL with Multiplication factor 1 - 31x
The PLL provides the possibility of multiplying a frequency by any number from 1 to 31. In com-
bination with the prescalers, this gives a wide range of output frequencies from all clock sources.
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8386A–AVR–07/11