CHAPTER 9 WATCHDOG TIMER
User’s Manual U13850EJ6V0UD
266
9.4.2 Operation as interval timer
Set bit 4 (WDTM4) to 0 in the watchdog timer mode register (WDTM) to operate the watchdog timer as an interval
timer that repeatedly generates interrupts with a preset count value as the interval.
When operating as an interval timer, the interrupt mask flag (WDTMK) of the WDTIC register and the priority
setting flag (WDTPR0 to WDTPR2) become valid, and a maskable interrupt (INTWDTM) can be generated. The
default priority of INTWDTM has the highest priority setting of the maskable interrupts.
The interval timer continues operating in the HALT mode and stops in the IDLE mode and STOP mode.
Therefore, before entering the IDLE mode/STOP mode, set the RUN bit of the WDTM register to 1 and clear the
interval timer. Then set the IDLE mode/STOP mode.
Cautions 1.
Once bit 4 (WDTM4) of WDTM is set to 1 (selecting the watchdog timer mode), the interval
timer mode is not entered as long as RESET is not input.
2.
The interval time immediately after being set by WDTM may be up to 2
10
/f
XX
seconds less than
the set time.
3. When the subclock is selected for the CPU clock, the watchdog timer stops (retains)
counting.
Table 9-5. Interval Time of Interval Timer
Interval Time
Clock
f
XX
= 20 MHz
Note
f
XX
= 12.58 MHz
2
14
/f
XX
819.2
µ
s
1.3 ms
2
15
/f
XX
1.6 ms
2.6 ms
2
16
/f
XX
3.3 ms
5.2 ms
2
17
/f
XX
6.6 ms
10.4 ms
2
18
/f
XX
13.1 ms
20.8 ms
2
19
/f
XX
26.2 ms
41.6 ms
2
20
/f
XX
52.4 ms
83.3 ms
2
22
/f
XX
209.7 ms
333.4 ms
Note
Only in the V850/SB1.
Содержание V850/SB1
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