Datasheet

 2018 Microchip Technology Inc. Data Sheet Complete DS40002058A-page 26
ATxmega128A1U/ATxmega64A1U
Figure 10-1. The clock system, clock sources, and clock distribution.
10.3 Clock Sources
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 characteristics and accuracy of the
internal oscillators, refer to the device datasheet.
Real Time
Counter
Peripherals
RAM AVR CPU
Non-Volatile
Memory
Watchdog
Timer
Brown-out
Detector
System Clock Prescalers
USB
Prescaler
System Clock Multiplexer
(SCLKSEL)
PLLSRC
RTCSRC
DIV32
32 kHz
Int. ULP
32.768 kHz
Int. OSC
32.768 kHz
TOSC
2 MHz
Int. Osc
32 MHz
Int. Osc
0.4 – 16 MHz
XTAL
DIV32 DIV32
DIV4
XOSCSEL
PLL
USBSRC
TOSC1 TOSC2 XTAL1 XTAL2
clk
SYS
clk
RTC
clk
PER2
clk
PER
clk
CPU
clk
PER4
clk
USB