Product data

HD404818 Series
36
• When the MCU is in watch mode or subactive mode, if the high level period before the falling edge of
INT
0
is shorter than the interrupt frame, INT
0
is not be detected. Also, if the low level period after the
falling edge of INT
0
is shorter than the interrupt frame, INT
0
is not be detected.
Edge detection is shown in figure 18. The level of the INT
0
signal is sampled by a sampling clock.
When this sampled value changes to low from high, a falling edge is detected.
In figure 19, the level of the INT
0
signal is sampled by an interrupt frame. In (a) the sampled value is
low at point A, and also low at point B. Therefore, a falling edge is not detected. In (b), the sampled
value is high at point A, and also high at point B. A falling edge is not detected in this case either.
When the MCU is in watch mode or subactive mode, keep the high level and low level period of INT
0
longer than the interrupt frame.
High Low
INT
Sampling
0
Low
Figure 18 Edge Detection
A: Low B: Low
INT
Interrupt
frame
0
A: High B: High
INT
Interrupt
frame
0
(a) High level period (b) Low level period
Figure 19 Sampling Example