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CHAPTER 4 APPLICATIONS OF WATCHDOG TIMER
Figure 4-4. Format of Watchdog Timer Mode Register
(
μ
PD78002, 78002Y, 78014, 78014Y, 78018F, 78018FY, 78014H subseries,
μ
PD780001)
Notes 1.
Once WDTM3 and WDTM4 have been set to 1, they cannot be cleared to 0 by software.
2.
When RUN is set to 1, the WDTM starts interval timer operation.
3.
Once RUN has been set to 1, it cannot be cleared to 0 by software. Therefore, when counting has been
started, it cannot be stopped by any means other than the RESET signal.
Cautions 1. When RUN is set to 1 and the watchdog timer is cleared, the actual overflow time is up to 0.5%
shorter than the time set by the timer clock select register 2 (TCL2).
2. When using the watchdog timer modes 1 and 2, confirm that the interrupt request flag (TMIF4)
is 0 and then set WDTM4 to 1.
If WDTM4 is set to 1 while TMIF4 is 1, the non-maskable interrupt occurs regardless of the
contents of WDTM3.
Remark
×
: don’t care
7
6
5
4
3
2
Symbol
1
0
WDTM4
Selects operation mode of watchdog timer
Note 1
FFF9H
0
WDTM
0
WDTM3
0
WDTM4
0
0
RUN
Address
At reset
R/W
00H
R/W
WDTM3
0
Interval timer mode (maskable interrupt
Note 2
request occurs when overflow occurs)
×
1
Watchdog timer mode 1 (non-maskable
interrupt request occurs when overflow occurs)
0
1
Watchdog timer mode 2 (reset operation
starts when overflow occurs)
1
RUN
Selects watchdog timer operation
Note 3
0
Stops counting
1
Clears counter and starts counting