UPD784020 Datasheet, PDF (42/90 Pages) NEC – 16/8-BIT SINGLE-CHIP MICROCOMPUTER

mPD784020, 784021
8.10 WATCHDOG TIMER
A watchdog timer is incorporated for CPU runaway detection. The watchdog timer, if not cleared by software within
a specified interval, generates a nonmaskable interrupt. Furthermore, once watchdog timer operation is enabled,
it cannot be disabled by software. The user can specify whether priority is placed on an interrupt based on the
watchdog timer or on an interrupt based on the NMI pin.
H
Fig. 8-13 Block Diagram of Watchdog Timer
fCLK
Timer
fCLK/2²¹
fCLK/2²⁰
fCLK/2¹⁹
fCLK/2¹⁷
INTWDT
Clear signal
42