HD404459 Datasheet, PDF (40/122 Pages) Renesas Technology Corp – 4-bit HMCS400-series microcomputers

HD404459 Series
Notes on Use:
• When the MCU is in watch mode or subactive mode, if the high level period before the falling edge of
INT₀ and WU₀–WU₇ is shorter than the interrupt frame, INT₀ and WU₀–WU₇ will not be detected.
Also, if the low level period after the falling edge of INT₀ and WU₀–WU₇ is shorter than the interrupt
frame, INT₀ and WU₀–WU₇ will not be detected.
Edge detection is shown in figure 23. The level of the INT₀ and WU₀–WU₇ signals are sampled by a
sampling clock. When this sampled value changes from high to low, a falling edge is detected.
In figure 24, the level of the INT₀ and WU₀–WU₇ signals are 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 will not be detected.
In (b), the sampled value is high at point A, and also high at point B. A falling edge will not be detected
in this case either.
When the MCU is in watch mode or subactive mode, keep the high level and low level periods of INT₀
and WU₀–WU₇ longer than interrupt frame.
INT₀,
WU₀–WU₇
Sampling
High
Low
Low
Figure 23 Edge Detection
INT₀,
WU₀–WU₇
INT₀,
WU₀–WU₇
Interrupt
frame
A: Low
B: Low
Interrupt
frame
A: High
B: High
a. High level period
b. Low level period
Figure 24 Sampling Example
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