CHAPTER 5 INTERRUPT/EXCEPTION PROCESSING FUNCTION
User’s Manual U13850EJ4V0UM
143
5.3.7 Watchdog timer mode register (WDTM)
Read/write is available in 8- or 1-bit units (for details, refer to
CHAPTER 9 WATCHDOG TIMER
).
Figure 5-14. Watchdog Timer Mode Register (WDTM) Format
After reset: 00H
R/W
Address: FFFFF384H
Symbol
<7>
6
5
4
3
2
1
0
WDTM
RUN
0
0
WDTM4
0
0
0
0
RUN
Watchdog timer operation control
0
Count operation stop
1
Count start after clearing
WDTM4
Timer mode selection/interrupt control by WDT
0
Interval timer mode
1
WDT mode
Caution If 1 is set to RUN or WDTM4 bit, no operation other than the reset input is available for clearing
this register.
5.3.8 Noise elimination
(1) Noise elimination of INTP0 to INTP3 pins
INTP0 to INTP3 pins incorporate the noise eliminator that functions via an analog delay. Therefore, a signal
input to each pin is not detected as an edge, unless it maintains its input level for a certain period.
An edge is detected after a certain period has elapsed.
(2) Noise elimination of INTP4 and INTP5 pins
INTP4 and INTP5 pins incorporate the digital noise eliminator. If an input level of the INTP pin is detected with
the sampling clock (f
XX
) and the same level is not detected three successive times, the input pulse is eliminated
as a noise. Note the followings:
•
In the case that the input pulse width is between 2 and 3 clocks, whether the input pulse is detected as a valid
edge or eliminated as a noise is indefinite.
•
To securely detect the level as a pulse, the same level input of 3 clocks
or more is required.
•
When a noise is generated in synchronization with a sampling clock, this may not be recognized as a noise.
In this case, eliminate the noise by adding a filter to the input pin.