UPD78F9418A NEC, UPD78F9418A Datasheet - Page 130

• Manufacturer Part Number: UPD78F9418A
• Description: (UPD7894xxA) 8-Bit Single Chip Microcontrollers
• Manufacturer: NEC

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8.2 Configuration of Watch Timer
130
2
2
2
2
2
2
Counter
Prescaler
Control register
(1)
(2)
The watch timer consists of the following hardware.
4
5
6
7
8
9
× 1/f
× 1/f
× 1/f
× 1/f
× 1/f
× 1/f
Watch timer
The 4.19 MHz main system clock or 32.768 kHz subsystem clock is used to issue an interrupt request
(INTWT) at 0.5-second intervals.
Caution When the main system clock is operating at 5.0 MHz, it cannot be used to generate a
Interval timer
The interval timer is used to generate an interrupt request (INTWT) at specified intervals.
Remark
W
W
W
W
W
W
Item
Interval
0.5-second interval. In this case, the subsystem clock, which operates at 32.768 kHz,
should be used instead.
f
f
f
W
X
XT
: Main system clock oscillation frequency
: Watch timer clock frequency (f
: Subsystem clock oscillation frequency
5 bits × 1
9 bits × 1
Watch timer mode control register (WTM)
409.6 µ s
819.2 µ s
1.64 ms
3.28 ms
6.55 ms
13.1 ms
Operation at f
Table 8-1. Interval Time of Interval Timer
Table 8-2. Configuration of Watch Timer
CHAPTER 8 WATCH TIMER
X
User’s Manual U13952EJ3V0UD
= 5.0 MHz
X
/2
7
or f
489 µ s
978 µ s
1.96 ms
3.91 ms
7.82 ms
15.6 ms
Operation at f
XT
Configuration
)
X
= 4.19 MHz
488 µ s
977 µ s
1.95 ms
3.91 ms
7.81 ms
15.6 ms
Operation at f
XT
= 32.768 kHz