HD404629R Datasheet, PDF (45/157 Pages) Renesas Technology Corp – AS Microcomputer Incorporating a DTMF Generator Circuit

HD404629R Series
Notes: 2. When the MCU is in watch mode or subactive mode, if the high level period before the falling
edge of INT₀ is shorter than the interrupt frame, INT₀ is not detected. Also, if the low level
period after the falling edge of INT₀ is shorter than the interrupt frame, INT₀ is not detected.
Edge detection is shown in figure 24. The level of the INT₀ signal is sampled by a sampling
clock. When this sampled value changes to low from high, a falling edge is detected.
In figure 25, the level of the INT₀ 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
INT₀ longer than interrupt frame.
INT₀
Sampling
High
Low
Low
Figure 24 Edge Detection
INT₀
INT₀
Interrupt
frame
A: Low
B: Low
Interrupt
frame
A: High
B: High
(a) High level period
Figure 25 Sampling Example
(b) Low level period
43