NEC mPD780208 Subseries, Руководство пользователя

Страница: 174 / 418

174
User’s Manual U11302EJ4V0UM
CHAPTER 9 WATCHDOG TIMER
9.1 Watchdog Timer Functions
The watchdog timer has the following functions.
• Watchdog timer
• Interval timer
Caution Select the watchdog timer mode or the interval timer mode using the watchdog timer mode
register (WDTM) (the watchdog timer and interval timer cannot be used at the same time).
(1) Watchdog timer mode
This mode detects an inadvertent program loop. Upon detection of the program loop, a non-maskable
interrupt request or RESET can be generated.
Table 9-1. Watchdog Timer Program Loop Detection Time
Program Loop When Operated at Program Loop When Operated at
Detection Time f
X
= 5.0 MHz Detection Time f
X
= 5.0 MHz
2 11 x 1/f
X
410
µ
s 2 15 x 1/f
X
6.55 ms
2 12 x 1/f
X
819
µ
s 2 16 x 1/f
X
13.1 ms
2 13 x 1/f
X
1.64 ms 2 17 x 1/f
X
26.2 ms
2 14 x 1/f
X
3.28 ms 2 19 x 1/f
X
104.9 ms
f
X
: Main system clock oscillation frequency
(2) Interval timer mode
Interrupt requests are generated at the preset time intervals.
Table 9-2. Interval Time
Interval Time
When Operated
Interval Time
When Operated at
at f
X
= 5.0 MHz f
X
= 5.0 MHz
2 12 x 1/f
X
819
µ
s 2 16 x 1/f
X
13.1 ms
2 13 x 1/f
X
1.64 ms 2 17 x 1/f
X
26.2 ms
2 14 x 1/f
X
3.28 ms 2 18 x 1/f
X
52.4 ms
2 15 x 1/f
X
6.55 ms 2 20 x 1/f
X
210 ms
f
X
: Main system clock oscillation frequency