60.6.3.7 Double Frequency Monitor

The double frequency monitor checks the two points below, assuming that the frequency of the 32.768 Crystal Oscillator (X32CK) is lower than the frequency of the 64 kHz RC Oscillator (ICLK) (typically f_ICLK = 64 kHz and f_X32CK = 32.768 kHz):

The number of ICLK periods in 16 X32CK periods must not exceed 48.
The number of X32CK periods in 32 ICLK periods must not exceed 34.

These values are calculated based on the extreme values of the frequency ranges.

Figure 60-15. Double Frequency Monitor Principle

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