168 User’s Manual U11302EJ4V0UMCHAPTER 8 WATCH TIMER8.1 Watch Timer FunctionsThe watch timer has the following functions.• Watch timer• Interval timerThe watch timer and the interval timer can be used simultaneously.(1) Watch timerWhen the 32.768 kHz subsystem clock is used, a flag (WTIF) is set at 0.5-second or 0.25-second intervals.In addition, when the 4.19 MHz (standard: 4.194304 MHz) main system clock is used, a flag (WTIF) is setat 0.5-second or 1-second intervals.Caution 0.5-second intervals cannot be generated with the 5.0 MHz main system clock. Switchto the 32.768 kHz subsystem clock to generate 0.5-second intervals.(2) Interval timerInterrupt requests (INTTM3) are generated at the preset time interval.Table 8-1. Interval Timer Interval TimeInterval Time When Operated When Operated at When Operated atat f X = 5.0 MHz f X = 4.19 MHz f XT = 32.768 kHz2 12 x 1/f X 819μs 978μs 488μs2 13 x 1/f X 1.64 ms 1.96 ms 977μs2 14 x 1/f X 3.28 ms 3.91 ms 1.95 ms2 15 x 1/f X 6.55 ms 7.82 ms 3.91 ms2 16 x 1/f X 13.1 ms 15.6 ms 7.81 ms2 17 x 1/f X 26.2 ms 31.3 ms 15.6 msf X : Main system clock oscillation frequencyf XT : Subsystem clock oscillation frequency
