void __low_power_mode_off_on_exit(void);
__low_power_mode_off_on_exit turns low power mode off when an interrupt returns, causing the halted CPU to resume in active mode with all clocks enabled.
__low_power_mode_off_on_exit can only be used in interrupt functions—an error is reported if it is used outside an interrupt function.
__low_power_mode_off_on_exit is an intrinsic function and produces inline code.