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Chapter 21 Hardware Watchdog Timer
4.Functions
4. Functions
If the watchdog timer is not cleared periodically, a setting initialization reset (INIT) occurs. In this case the
value of registers in CPU is not guaranteed.
● Function of the hardware watchdog timer
After releasing INITX the hardware watchdog timer starts immediately without stabilization time. If the timer is
not cleared periodically, setting initialization (INIT) reset occurs.
● Period of the hardware watchdog timer
The timer width is 16-bit. Since the RC oscillator is used as clock source of the hardware watchdog timer, the
duration of the timer deviates with the RC oscillator accuracy:
Note: The watchdog duration elongation (ED1-0) setting is not available on MB91V460. In that case ED1-0 is
always “00”.
ED1-0 Min. Typ. Max.
RC oscillation cycle (u s) 5 10 20
Watchdog term (ms)
00 327.68 655.36 1310.72
01 655.36 1310.72 2621.44
10 1310.72 2621.44 5242.88
11 2621.44 5242.88 10485.76
