UPD70F3212 Datasheet, PDF (390/861 Pages) NEC – 32-Bit Single-Chip Microcontrollers

CHAPTER 11 INTERVAL TIMER, WATCH TIMER
11.2.4 Operation
(1) Operation as watch timer
The watch timer generates an interrupt request at fixed time intervals. The watch timer operates using time
intervals of 0.25 or 0.5 seconds with the subclock (32.768 kHz).
The count operation starts when the WTM.WTM0 and WTM.WTM1 bits are set to 11. When these bits are
cleared to 00, the 10-bit prescaler and 5-bit counter are cleared and the count operation stops.
The 5-bit counter can be cleared to synchronize the time by clearing the WTM1 bit to 0 when the watch timer
and interval timer WT operate simultaneously. At this time, an error of up to 15.6 ms may occur in the watch
timer, but interval timer WT is not affected.
(2) Operation as interval timer
The watch timer can also be used as an interval timer that repeatedly generates an interrupt request signal
(INTWTI) at intervals specified by a count value set in advance.
The interval time can be selected by the WTM.WTM4 to WTM.WTM7 bits.
Table 11-1. Interval Time of Interval Timer
WTM7
WTM6
WTM5
WTM4
0
0
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
0
0
1
0
1
0
1
1
0
0
1
1
1
1
0
0
0
1
0
0
1
1
0
1
0
1
0
1
1
1
1
0
0
1
1
0
1
1
1
1
0
1
1
1
1
Remark fW: Watch timer clock frequency
2⁴ × 1/fW
2⁵ × 1/fW
2⁶ × 1/fW
2⁷ × 1/fW
2⁸ × 1/fW
2⁹ × 1/fW
2¹⁰ × 1/fW
2¹¹ × 1/fW
2⁴ × 1/fW
2⁵ × 1/fW
2⁶ × 1/fW
2⁷ × 1/fW
2⁸ × 1/fW
2⁹ × 1/fW
2¹⁰ × 1/fW
2¹¹ × 1/fW
Interval Time
488 µs (operating at fW = fXT = 32.768 kHz)
977 µs (operating at fW = fXT = 32.768 kHz)
1.95 ms (operating at fW = fXT = 32.768 kHz)
3.91 ms (operating at fW = fXT = 32.768 kHz)
7.81 ms (operating at fW = fXT = 32.768 kHz)
15.6 ms (operating at fW = fXT = 32.768 kHz)
31.3 ms (operating at fW = fXT = 32.768 kHz)
62.5 ms (operating at fW = fXT = 32.768 kHz)
488 µs (operating at fW = fBRG = 32.768 kHz)
977 µs (operating at fW = fBRG = 32.768 kHz)
1.95 ms (operating at fW = fBRG = 32.768 kHz)
3.91 ms (operating at fW = fBRG = 32.768 kHz)
7.81 ms (operating at fW = fBRG = 32.768 kHz)
15.6 ms (operating at fW = fBRG = 32.768 kHz)
31.3 ms (operating at fW = fBRG = 32.768 kHz)
62.5 ms (operating at fW = fBRG = 32.768 kHz)
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User’s Manual U16890EJ1V0UD