ATXMEGA256A3B_09 ATMEL [ATMEL Corporation], ATXMEGA256A3B_09 Datasheet - Page 19

• Manufacturer Part Number: ATXMEGA256A3B_09
• Description: 8/16-bit XMEGA A3B Microcontroller
• Manufacturer: ATMEL [ATMEL Corporation]

10.3
10.3.1
10.3.2
8116F–AVR–09/09
Clock Options
32 kHz Ultra Low Power Internal Oscillator
32.768 kHz Calibrated Internal Oscillator
Figure 10-1. Clock system overview
Each clock source is briefly described in the following sub-sections.
The 32 kHz Ultra Low Power (ULP) Internal Oscillator is a very low power consumption clock
source. It is used for the Watchdog Timer, Brown-Out Detection and as an asynchronous clock
source for the Real Time Counter. This oscillator cannot be used as the system clock source,
and it cannot be directly controlled from software.
The 32.768 kHz Calibrated Internal Oscillator is a high accuracy clock source that can be used
as the system clock source or as an asynchronous clock source for the Real Time Counter. It is
calibrated during production to provide a default frequency which is close to its nominal
frequency.
Run-Time Calibrated
Run-time Calibrated
Calibrated Internal
Internal Oscillator
Internal Oscillator
Internal Oscillator
Crystal Oscillator
Crystal Oscillator
0.4 - 16 MHz
32 kHz ULP
32.768 KHz
32.768 kHz
Clock Input
Oscillator
External
32 MHz
2 MHz
CLOCK CONTROL
with PLL and
Prescaler
UNIT
clk
clk
clk
clk
CPU
ULP
RTC
PER
XMEGA A3B
PERIPHERALS
NVM MEMORY
INTERRUPT
WDT/BOD
EEPROM
PORTS
EVSYS
FLASH
DMA
RAM
RTC
ADC
DAC
CPU
...
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