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 runaway. When a runaway is detected, a non-maskable
interrupt or the RESET signal can be generated.
Table 9-1. Watchdog Timer Runaway Detection Time
Runaway Detection Time
11 × 1/fX
At fX = 5.0 MHz
2
2
2
2
410 µs
13 × 1/fX
15 × 1/fX
17 × 1/fX
1.64 ms
6.55 ms
26.2 ms
fX: 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 fX = 5.0 MHz
2
2
2
2
11 × 1/fX
13 × 1/fX
15 × 1/fX
17 × 1/fX
410 µs
1.64 ms
6.55 ms
26.2 ms
fX: Main system clock oscillation frequency
User’s Manual U15075EJ1V0UM00
177
NEC [ NEC ]
