M16CSLASH29 datasheet(352/499 Pages) RENESAS

352 / 499 page

19. Programmable I/O Ports

page 328

Figure 19.12 Functioning of Digital Debounce Filter

P17

Data Bus

1. (Condition after reset). P17DDR=FF16. Pin input signal will be output directly.

2. Set the P17DDR register to 0316. The P17DDR register starts decrement along the f8 as a counter source, if the pin

input level (e.g.,"L") and the signal output level (e.g.,"H") are not matched.

3. The P17DDR register will stops counting when the pin input level and the signal output level are matched (e.g.,

both levels are "H") while counting.

4. If the pin input level (e.g.,"L") and the signal output level (e.g.,"H") are not matched the P17DDR register will start

decrement again after the setting value is reloaded.

5. When the P17DDR register is underflow, it stops counting and the signal output will output the same as pin input

level (e.g."L").

6. If the pin input level (e.g.,"H") and the signal output level (e.g., "L") are not matched again, the P17DDR register will

start decrement again after the setting value is reloaded.

7. When the P17DDR register is underflow, it stops counting and the signal output will output the same as pin input

level (e.g."H").

8. If the pin input level (e.g.,"H") and the signal output level (e.g., "L") are not matched again, the P17DDR register will

start decrement again after the setting value is reloaded.

9. Set the P17DDR register to FF16. The P17DDR register starts counting after the setting value is reloaded. Pin input

signal will be output directly.

Clock

Port In

Reload Value

(write)

Digital Debounce Filter

Signal Out

Count Value

(read)

To INT5

Data Bus

Reload Value

Port In

Signal Out

Count Value

Reload Value

(continued)

Port In

(continued)

Signal Out

(continued)

Count Value

(continued)

•

Example of INT5 Digital Debounce Function (if P17DDR = 0316)

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