ATXMEGA32A4_14 Datasheet, PDF (19/108 Pages) ATMEL Corporation – Non-volatile Program and Data Memories

XMEGA A4
Figure 10-1. Clock system overview
32 kHz ULP
Internal Oscillator
32.768 kHz
Calibrated Internal
Oscillator
2 MHz
Run-Time Calibrated
Internal Oscillator
32 MHz
Run-time Calibrated
Internal Oscillator
32.768 KHz
Crystal Oscillator
0.4 - 16 MHz
Crystal Oscillator
External
Clock Input
clk_ULP
WDT/BOD
clk_RTC
RTC
PERIPHERALS
ADC
DAC
CLOCK CONTROL
UNIT
clk_PER
with PLL and
Prescaler
PORTS
...
DMA
INTERRUPT
EVSYS
RAM
CPU
clk_CPU NVM MEMORY
FLASH
EEPROM
Each clock source is briefly described in the following sub-sections.
10.3 Clock Options
10.3.1 32 kHz Ultra Low Power Internal Oscillator
10.3.2
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.
32.768 kHz Calibrated Internal Oscillator
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.
8069R–AVR–06/2013
19
Not recommended for new designs -
Use XMEGA A4U series