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Chapter 7 AC Zero-Cross Circuit/Noise Filter
125
Noise Filter
7-3-2 Example Input and Output Waveforms for Noise Filter
When the noise filter is used, the waveform input to the IRQ0 pin is sampled based on the
clock specified by the NF0CKS0 and NF0CKS1 flags of the noise filter control register
(NFCTR). The waveform input to the IRQ1 pin is also sampled based on the clock specified
by the NF1CKS0 and NF1CKS1 flags. If the sampled level remains the same for 3
consecutive samples, it is sent the CPU; otherwise, the previous level is maintained.
Figure 7-3-2 Noise Filter Input and Output Waveform Example
Noise filtering cannot be
used in the STOP or HALT
modes.
Sampling
Input
Waveform after
noise filtering
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