Chapter 9 Watchdog Timer; Watchdog Timer Functions; Watchdog Timer Program Loop Detection Time; Interval Time - NEC PD789488 User Manual

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.
11
× 1/f
2
13
× 1/f
2
15
× 1/f
2
17
× 1/f
2
f : Main system clock oscillation frequency
X
(2) Interval timer
The interval timer generates an interrupt at an arbitrary preset interval.
11
2 × 1/f
13
2 × 1/f
15
× 1/f
2
17
× 1/f
2
f : Main system clock oscillation frequency
X

CHAPTER 9 WATCHDOG TIMER

Table 9-1. Watchdog Timer Program Loop Detection Time
Program Loop Detection Time
X
X
X
X
Table 9-2. Interval Time
Interval
X
X
X
X
User's Manual U15331EJ4V1UD
At f = 5.0 MHz
X
µ
410 s
1.64 ms
6.55 ms
26.2 ms
At f = 5.0 MHz
X
µ
410 s
1.64 ms
6.55 ms
26.2 ms
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