UPD784224 Datasheet, PDF (45/92 Pages) NEC – 16/8-BIT SINGLE-CHIP MICROCONTROLLERS

µPD784224, 784225, 784224Y, 784225Y
Figure 7-16. Block Diagram of Watch Timer
fXX/2⁷
fXT
fW
Prescaler
fW fW fW fW fW fW
2⁴ 2⁵ 2⁶ 2⁷ 2⁸ 2⁹
fW
2¹⁴
5-bit counter
fW
2⁵
INTWT
INTTM3
To 16-bit timer/counter
7.12 Watchdog Timer
A watchdog timer is provided to detect a hang up of the CPU. This watchdog timer generates a non-maskable
or maskable interrupt unless it is cleared by software within a specified interval time. Once enabled to operate, the
watchdog timer cannot be stopped by software. Whether the interrupt by the watchdog timer or the interrupt input
from the NMI pin takes precedence can be specified.
Figure 7-17. Block Diagram of Watchdog Timer
fCLK
RUN^Note
HALT
IDLE
STOP
Timer
fCLK/2²¹
fCLK/2²⁰
fCLK/2¹⁹
fCLK/2¹⁷
INTWDT
Note Write 1 to bit 7 (RUN) of the watchdog timer (WDM).
Remark fCLK: Internal system clock (fXX to fXX/8)
Data Sheet U12376EJ1V0DS00
45