CHAPTER 9 WATCHDOG TIMER
User’s Manual U13850EJ4V0UM
242
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 STOP mode and IDLE mode.
Therefore, after the RUN bit of WDTM register is set to 1 and the interval timer is cleared before entering the STOP
mode/IDLE mode, execute the STOP instruction.
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 sub clock 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 for the V850/SB1.
Содержание MPD703030A
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