Datasheet

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Data Sheet 50 1999-07
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Figure 13 External Clock Drive XTAL1
Note: The main oscillator is optimized for oscillation with a crystal within a frequency
range of 4...16 MHz. When driven by an external clock signal it will accept the
specified frequency range. Operation at lower input frequencies is possible but is
guaranteed by design only (not 100% tested).
It is strongly recommended to measure the oscillation allowance (or margin) in the
final target system (layout) to determine the optimum parameters for the oscillator
operation.