UPD78F0138 NEC, UPD78F0138 Datasheet - Page 235

• Manufacturer Part Number: UPD78F0138
• Description: (UPD78xxxx) 8-Bit Single-Chip Microcontrollers
• Manufacturer: NEC

9.4.2 Interval timer operation
the preset count value.
(WTM).
stops.
WTM6
The watch timer operates as interval timer which generates interrupt requests (INTWTI) repeatedly at an interval of
The interval time can be selected with bits 4 to 6 (WTM4 to WTM6) of the watch timer operation mode register
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
Remark
Remark
0
0
0
0
1
1
1
1
Count clock
Watch timer
interrupt INTWT
Interval timer
interrupt INTWTI
WTM5
0
0
1
1
0
0
1
1
f
f
f
f
n:
Figures in parentheses are for operation with f
X
XT
W
W
: X1 input clock oscillation frequency
: Watch timer clock frequency
: Watch timer clock frequency
: Subsystem clock oscillation frequency
5-bit counter
The number of times of interval timer operations
WTM4
0
1
0
1
0
1
0
1
Figure 9-3. Operation Timing of Watch Timer/Interval Timer
2
2
2
2
2
2
2
2
4
5
6
7
8
9
10
11
/f
/f
/f
/f
/f
/f
/f
/f
W
W
W
W
W
W
W
W
Start
Interval Time
0H
Table 9-5. Interval Timer Interval Time
Interrupt time of watch timer (0.5 s)
Interval time
(T)
CHAPTER 9 WATCH TIMER
User’s Manual U16228EJ2V0UD
n
T
488
977
1.95 ms
3.91 ms
7.81 ms
15.6 ms
31.3 ms
62.5 ms
f
W
XT
= 32.768 kHz (WTM7 = 1, WTM3, WTM2 = 0, 0)
= 32.768 kHz (WTM7 = 1)
µ
µ
s
s
When Operated at
Overflow
Interrupt time of watch timer (0.5 s)
T
n
205
410
820
1.64 ms
3.28 ms
6.55 ms
13.1 ms
26.2 ms
T
f
X
µ
µ
µ
= 10 MHz (WTM7 = 0)
s
s
s
When Operated at
Overflow
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