AVR1003: Using the XMEGA™ Clock System: The user is responsible for providing a minimum input clock frequency of 0.44 MHz to
the PLL and make sure that the output never exceeds 200 MHz. The minimum input
frequency requirement applies when using an external clock signal as input to the
PLL.
+
Note that when using the
PLL, the user is responsible for not exceeding recommended frequency limits for the
CPU and peripherals.

The R32M oscillator can be used as a system clock source directly or through the
internal PLL to generate even higher system frequencies. 32*31=992MHz - ARM9 отдыхает