NEC PD78F9488 - Manual (Page 167)

User’s Manual U15331EJ4V1UD
167
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 interval timer mode by using the watchdog timer mode
register (WDTM).
(1) Watchdog
timer
The watchdog timer is used to detect a program loop. When a program loop is detected, a non-maskable
interrupt or the RESET signal can be generated.
Table 9-1. Watchdog Timer Program Loop Detection Time
Program Loop Detection Time At f
X
= 5.0 MHz
2 11 × 1/f
X
410 µ s
2 13 × 1/f
X
1.64 ms
2 15 × 1/f
X
6.55 ms
2 17 × 1/f
X
26.2 ms
f
X
: Main system clock oscillation frequency
(2) Interval timer
The interval timer generates an interrupt at an arbitrary preset interval.
Table 9-2. Interval Time
Interval At f
X
= 5.0 MHz
2 11 × 1/f
X
410 µ s
2 13 × 1/f
X
1.64 ms
2 15 × 1/f
X
6.55 ms
2 17 × 1/f
X
26.2 ms
f
X
: Main system clock oscillation frequency