uPD789074 Subseries 8-Bit Single-Chip Microcontrollers UD - Home

CHAPTER 8 WATCHDOG TIMER8.1 Watchdog Timer FunctionsThe watchdog timer has the following functions.• Watchdog timer• Interval timerCaution Select the watchdog timer mode or interval timer mode by using the watchdog timer moderegister (WDTM).(1) Watchdog timerThe watchdog timer is used to detect inadvertent program loops. When an inadvertent loop is detected, anon-maskable interrupt or a RESET signal can be generated.Table 8-1. Inadvertent Loop Detection Time of Watchdog TimerInadvertent Loop Detection Time At fX = 10.0 MHz Operation Note At fX = 5.0 MHz Operation2 11 × 1/fX 205 µs 410 µs2 13 × 1/fX 819 µs 1.64 ms2 15 × 1/fX 3.28 ms 6.55 ms2 17 × 1/fX 13.1 ms 26.2 msNote Expanded-specification products only.RemarkfX: System clock oscillation frequency(2) Interval timerThe interval timer generates an interrupt at an arbitrary preset interval.Table 8-2. Interval TimeInterval Time At fX = 10.0 MHz Operation Note At fX = 5.0 MHz Operation2 11 × 1/fX 205 µs 410 µs2 13 × 1/fX 819 µs 1.64 ms2 15 × 1/fX 3.28 ms 6.55 ms2 17 × 1/fX 13.1 ms 26.2 msNote Expanded-specification products only.RemarkfX: System clock oscillation frequencyUser’s Manual U14801EJ3V1UD 109