ATXMEGA128B3-AU ATMEL [ATMEL Corporation], ATXMEGA128B3-AU Datasheet - Page 21

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

10.3
8074B–AVR–02/12
Clock Sources
Figure 10-1. The Clock system, clock sources and clock distribution.
The clock sources are divided in two main groups: internal oscillators and external clock
sources. Most of the clock sources can be directly enabled and disabled from software, while
others are automatically enabled or disabled, depending on peripheral settings. After reset, the
device starts up running from the 2MHz internal oscillator. The other clock sources, DFLLs and
PLL, are turned off by default.
The internal oscillators do not require any external components to run. For details on character-
istics and accuracy of the internal oscillators, refer to the device datasheet.
Brown-out
Detector
LCD
clk
LCD
Watchdog
Int. ULP
32 kHz
Timer
Real Time
Counter
clk
32.768 kHz
Int. OSC
RTC
RTCSRC
Peripherals
32.768 kHz
TOSC
clk
PER4
clk
XOSCSEL
PER2
clk
PER
0.4 – 16 MHz
System Clock Prescalers
System Clock Multiplexer
XTAL
RAM
clk
(SCLKSEL)
SYS
32 MHz
Int. Osc
PLLSRC
PLL
AVR CPU
XMEGA B3
clk
Int. Osc
2 MHz
CPU
clk
Non-Volatile
Prescaler
Memory
USB
USBSRC
USB
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