ATXMEGA256A3B_09 ATMEL [ATMEL Corporation], ATXMEGA256A3B_09 Datasheet - Page 18

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

10. System Clock and Clock options
10.1
10.2
8116F–AVR–09/09
Features
Overview
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XMEGA A3B has an advanced clock system, supporting a large number of clock sources. It
incorporates both integrated oscillators, external crystal oscillators and resonators. A high fre-
quency Phase Locked Loop (PLL) and clock prescalers can be controlled from software to
generate a wide range of clock frequencies from the clock source input.
It is possible to switch between clock sources from software during run-time. After reset the
device will always start up running from the 2 Mhz internal oscillator.
A calibration feature is available, and can be used for automatic run-time calibration of the inter-
nal 2 MHz and 32 MHz oscillators. This reduce frequency drift over voltage and temperature.
A Crystal Oscillator Failure Monitor can be enabled to issue a Non-Maskable Interrupt and
switch to internal oscillator if the external oscillator fails.
cipal clock system in XMEGA A3B.
Fast start-up time
Safe run-time clock switching
Internal Oscillators:
External clock options
PLL with internal and external clock options with 2 to 31x multiplication
Clock Prescalers with 2 to 2048x division
Fast peripheral clock running at 2 and 4 times the CPU clock speed
Automatic Run-Time Calibration of internal oscillators
Crystal Oscillator failure detection
– 32 MHz run-time calibrated RC oscillator
– 2 MHz run-time calibrated RC oscillator
– 32.768 kHz calibrated RC oscillator
– 32 kHz Ultra Low Power (ULP) oscillator
– 0.4 - 16 MHz Crystal Oscillator
– 32 kHz Crystal Oscillator
– External clock
Figure 10-1 on page 19
XMEGA A3B
shows the prin-
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