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Watchdog Timer
12-2
12.1 Overview
This microcontroller has a 25-bit binary counter built in that can be used as a 16- to 25-bit watchdog timer.
A watchdog timer overflow generates a nonmaskable interrupt, enabling the watchdog timer overflow to be identified.
The watchdog timer is also used as an oscillation stabilization wait timer.
12.2 Features
• The number of bits in the binary counter is selectable.
When the CKSEL pin input is "H" (oscillating frequency: 8 MHz to 18 MHz):
16, 18, 20, 22, or 24 bits can be selected.
When the CKSEL pin input is "L" (oscillating frequency: 8 MHz to 20 MHz):
17, 19, 21, 23, or 25 bits can be selected.
Overflow cycle: 4.369 ms to 1118.481 ms
(when the
CKSEL
pin input is "H" and the oscillating frequency is 15 MHz)
• A non-maskable interrupt is generated when a watchdog timer overflow occurs.
• Watchdog timer overflow output
A flag can be set to "1" when a watchdog timer overflow occurs.
The watchdog timer overflow output can be selected as either pulse output or level output.
• Oscillation stabilization wait time (when the
CKSEL
pin input is "H" and the oscillating frequency is
15 MHz)
When reset is released: 17.476 ms
When recovering from STOP mode: 4.369 ms to 1118.481 ms
<Recommended value is 14 ms or longer.>
• The chip can self-reset internally by writing the RSTCTR register.