Chapter 7 Watchdog Timer; Watchdog Timer Functions; Inadvertent Loop Detection Time Of Watchdog Timer; Interval Time - NEC switch User Manual

7.1 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 inadvertent program loops. When an inadvertent loop is detected, a non-
maskable interrupt or the RESET signal can be generated.
Table 7-1. Inadvertent Loop Detection Time of Watchdog Timer
f
(2) Interval timer
The interval timer generates an interrupt at arbitrary intervals set in advance.
f
CHAPTER 7
Inadvertent Loop
Detection Time
× 1/f
11
2
X
× 1/f
13
2
X
× 1/f
15
2
X
× 1/f
17
2
X
: System clock oscillation frequency
X
Table 7-2. Interval Time

Interval Time

× 1/f
11
2
X
× 1/f
13
2
X
× 1/f
15
2
X
× 1/f
17
2
X
: System clock oscillation frequency
X
User's Manual U12978EJ3V0UD
WATCHDOG TIMER
Operation at f = 6.0 MHz
X
341 µ s
1.37 ms
5.46 ms
21.8 ms
Operation at f = 6.0 MHz
X
341 µ s
1.37 ms
5.46 ms
21.8 ms
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