UPD17227 datasheet(39/84 Pages) NEC

Part #	UPD17227

Description	4-BIT SINGLE-CHIP MICROCONTROLLER FOR SMALL GENERAL-PURPOSE INFRARED REMOTE CONTROL TRANSMITTER

PDF	84 Pages

Scroll/Zoom	100%

Manufacturer	NEC [NEC]

Direct Link	http://www.nec.com/

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39 / 84 page

µPD17225, 17226, 17227, 17228

Data Sheet U12643EJ2V0DS00

6.3

Operation Timing for Watchdog Timer

The basic interval timer can be used as a watchdog timer.

Unless the watchdog timer is reset within a fixed time

Note, it judges that “the program has hung up”, and the

µPD17225

is reset. It is therefore necessary to reset through programming the watchdog timer with in a fixed time.

The watchdog timer can be reset by setting WDTRES to 1.

Note

Fixed time: approx. 340 ms (at 4 MHz)

Cautions 1. The watchdog timer cannot be reset in the shaded range in Figure 6-2. Therefore, set

WDTRES before both the fX/2

21 and fX/220 signals go high.

2. Refer to 9. RESET for the WDOUT pin function.

Figure 6-2.

Watchdog Timer Operation Timing

fX/218

INTBTM (fX/220)

INTBTM (fX/218)

WDOUT

WDTRES

Watchdog timer

reset signal

WDOUT output goes low

if WDTRES is not set

Setting WDTRES at

this timing is invalid

fX/219

fX/220

fX/221

UPD17227 Datasheet(PDF) 39 Page - NEC