Interval Timer Operation - NEC 78K0/KD1 Series User Manual

9.4.2 Interval timer operation

The watch timer operates as interval timer which generates interrupt requests (INTWTI) repeatedly at an interval of
the preset count value.
The interval time can be selected with bits 4 to 6 (WTM4 to WTM6) of the watch timer operation mode register
(WTM).
When bit 0 (WTM0) of the WTM is set to 1, the count operation starts. When this bit is set to 0, the count operation
stops.
WTM6 WTM5 WTM4
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
Remark f : X1 input clock oscillation frequency
X
f : Subsystem clock oscillation frequency
XT
f : Watch timer clock frequency
W
CHAPTER 9 WATCH TIMER
Table 9-5. Interval Timer Interval Time
Interval Time
4
2 /f
W
5
2 /f
W
6
2 /f
W
7
2 /f
W
8
2 /f
W
9
2 /f
W
10
2 /f
W
11
2 /f
W
Preliminary User's Manual U16315EJ1V0UD
When Operated at
f = 32.768 kHz (WTM7 = 1)
XT
488 µ s
977 µ s
1.95 ms
3.91 ms
7.81 ms
15.6 ms
31.2 ms
62.4 ms
When Operated at
f = 10 MHz (WTM7 = 0)
X
205 µ s
410 µ s
820 µ s
1.64 ms
3.28 ms
6.55 ms
13.1 ms
26.2 ms
207