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8331B–AVR–03/12
Atmel AVR XMEGA AU
• Issue a non-maskable interrupt (NMI)
If the PLL or external clock source fails when not being used for the system clock, it is automati-
cally disabled, and the system clock will continue to operate normally. No NMI is issued. The
failure monitor is meant for external clock sources above 32kHz. It cannot be used for slower
external clocks.
When the failure monitor is enabled, it will not be disabled until the next reset.
The failure monitor is stopped in all sleep modes where the PLL or external clock source are
stopped. During wake up from sleep, it is automatically restarted.
The PLL and external clock source failure monitor settings are protected by the configuration
change protection mechanism, employing a timed write procedure for changing the settings. For
details, refer to
