ATXMEGA128B3-AU ATMEL [ATMEL Corporation], ATXMEGA128B3-AU Datasheet - Page 22

• Manufacturer Part Number: ATXMEGA128B3-AU
• Description: 8/16-bit Atmel XMEGA B3 Microcontroller
• Manufacturer: ATMEL [ATMEL Corporation]

10.3.1
10.3.2
10.3.3
10.3.4
10.3.5
10.3.6
10.3.7
8074B–AVR–02/12
32kHz Ultra Low Power Internal Oscillator
32.768kHz Calibrated Internal Oscillator
32.768kHz Crystal Oscillator
0.4 - 16MHz Crystal Oscillator
2MHz Run-time Calibrated Internal Oscillator
32MHz Run-time Calibrated Internal Oscillator
External Clock Sources
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 1kHz output. The oscillator is automatically
enabled/disabled when it is used as clock source for any part of the device. This oscillator can
be selected as the clock source for the RTC and for LCD.
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. This oscilla-
tor can be used as a clock source for the system clock, RTC and LCD, and as the DFLL
reference clock.
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 volt-
age swing on TOSC2 is available. This oscillator can be used as a clock source for the system
clock, RTC and LCD, and as the DFLL reference clock.
This oscillator can operate in four different modes optimized for different frequency ranges, all
within 0.4MHz - 16MHz.
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 close to its nominal frequency. A
DFLL can be enabled for automatic run-time calibration of the oscillator to compensate for tem-
perature and voltage drift and optimize the oscillator accuracy.
The 32MHz run-time calibrated internal oscillator is a high-requency oscillator. It is calibrated
during production to provide a default frequency close to its nominal frequency. A digital fre-
quency 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 oscilla-
tor can also be adjusted and calibrated to any frequency between 30MHz and 55MHz. The
production signature row contains 48MHz calibration values intended used when the oscillator is
used a full-speed USB clock source.
The XTAL1 and XTAL2 pins can be used to drive an external oscillator, either a quartz crystal or
a ceramic resonator. XTAL1 or each pin of port C can be used as input for an external clock sig-
nal. The TOSC1 and TOSC2 pins are dedicated to driving a 32.768kHz crystal oscillator.
XMEGA B3
22