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CodeVisionAVR
If an External Oscillator or Clock is used as System Clock Source, the following specific
configuration options are available:
The External Clock option specifies the value of the external clock frequency in kHz.
The External Clock Source - Start-up Time list box allows to select the type of external clock source:
external clock signal, crystal or ceramic resonator, and it's start-up time.
If the External Clock Source Failure Monitor option is enabled, the device will perform the following
actions if the external clock stops:
• switch to the 2MHz internal oscillator, independently of any clock system lock setting, by reseting
the System Clock Selection Register to it's default value
• reset the Oscillator Control Register Register to it's default value
• Set the External Clock Source Failure Detection Interrupt Flag in the XOSC Failure Detection
Register
• Issue a Non-Maskable Interrupt (NMI).
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