UPD784907 Datasheet, PDF (49/98 Pages) NEC – 16-BIT SINGLE-CHIP MICROCONTROLLER

µPD784907, 784908
8.10 Edge Detection Function
The interrupt input pins (NMI, INTP0 through INTP5) are used not only to input interrupt requests but also to input
trigger signals to the internal hardware units. Because these pins operate at the edge of the input signal, they have
an edge-detection function incorporated. Moreover, a noise elimination function is also provided to prevent erroneous
edge detection caused by noise.
Table 8-4. Noise Elimination Method of Interrupt Input Pins
Pin Name
NMI
INTP0 to INTP3
INTP4, INTP5
Detectable Edge
Noise Elimination Method
Rising edge or falling edge
Analog delay
Rising edge or falling edge, or both edges Clock sampling^Note
Analog delay
Note INTP0 is used for sampling clock selection.
8.11 Watchdog Timer
A watchdog timer is incorporated to detect a CPU runaway. The watchdog timer, if not cleared by software within
a specified interval, generates a non-maskable interrupt request. Furthermore, once watchdog timer operation is
enabled, it cannot be disabled by software. The user can specify whether priority is placed on an interrupt request
based on the watchdog timer or on an interrupt request based on the NMI pin.
Figure 8-15. Block Diagram of Watchdog Timer
fCLK
Timer
fCLK/2²¹
fCLK/2²⁰
fCLK/2¹⁹
fCLK/2¹⁷
INTWDT
Clear signal
Data Sheet U11680EJ2V0DS00
49