Panasonic MN101C77C - Manual (Page 146)

Chapter 3 Interrupts
III - 52 External Interrupts
Figure 3-3-8 Noise Remove Function Operation
■ Noise Remove Function Operation (External interrupts 0 to 4)
After sampling the input signal to the external interrupt pins ( IRQ0 to IRQ4) by the set sampling time, if the
same level comes continuously three times, that level is sent to the inside of LSI. If the same level does not
come continuously three times, the previous level is sent. It means that only the signal with the width of
more than " Sampling time X 3 sampling clock " can pass through the noise filter, and other much narrower
signals are removed, because those are regarded as noise.
Noise filter can not be used at STOP mode, HALT mode and SLOW mode.
Sampling
timing
IRQn pin input signal
Waveform after
filtering noise
0 0 1 1 1 1 1 0 0