UPD784044 Datasheet, PDF (39/90 Pages) NEC – 16-BIT SINGLE-CHIP MICROCONTROLLER

µPD784044(A), 784046(A)
7.7 Edge Detection Circuit
The interrupt input pins (NMI and INTP0 through INTP6) input not only interrupt requests but also trigger
signals of the internal hardware. Because all the interrupts and internal hardware operate by detecting specific
edges of the input signals, a function to detect edges is provided. In addition, a noise rejection function is also
provided to prevent detection of a wrong edge due to noise.
Pin
NMI
INTP0-INTP6
Detectable Edge
Either rising or falling edge
Either rising or falling edge, or both edges
Note A sampling clock can be selected.
Noise Rejected by:
Analog delay
Clock sampling^Note
7.8 Watchdog Timer
A watchdog timer is provided to detect a hang-up of the CPU. This watchdog timer generates a non-maskable
interrupt unless it is cleared by software within a specified interval time. Once the watchdog timer has been
enable to operate, its operation cannot be stopped by software. Moreover, it can be specified whether the
interrupt by the watchdog timer or the interrupt from the NMI pin takes precedence.
Figure 7-10. Block Diagram of Watchdog Timer
fCLK/2⁹
fCLK/2¹¹
fCLK
Divider
fCLK/2¹²
fCLK/2¹³
Watchdog timer (8 bits)
Overflow
INTWDT
WDT CLR
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