PD17225_15 Datasheet, PDF (41/86 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCONTROLLER FOR SMALL GENERAL-PURPOSE INFRARED REMOTE CONTROL TRANSMITTER

µPD17225, 17226, 17227, 17228
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/2²¹ 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
fX/2¹⁹
fX/2²⁰
fX/2²¹
INTBTM (fX/2²⁰)
INTBTM (fX/2¹⁸)
WDOUT
Watchdog timer
reset signal
WDTRES
Setting WDTRES at
this timing is invalid
WDOUT output goes low
if WDTRES is not set
Data Sheet U12643EJ2V0DS00
39