Configuration Of Watch Timer - NEC 78K0 Series User Manual

(1) Watch timer
When the peripheral hardware clock or subsystem clock is used, interrupt request signals (INTWT) are
generated at preset intervals.
Interrupt Time When Operated at
f = 32.768 kHz
SUB
µ
4
2 /f 488 s
W
µ
5
2 /f 977 s
W
13
2 /f 0.25 s
W
14
2 /f 0.5 s
W
Remark f : Peripheral hardware clock frequency
PRS
f : Subsystem clock frequency
SUB
f : Watch timer clock frequency (f
W
(2) Interval timer
Interrupt request signals (INTWTI) are generated at preset time intervals.
Interval Time When Operated at
f = 32.768 kHz
SUB
µ
4
2 /f 488 s
W
µ
5
2 /f 977 s
W
6
2 /f 1.95 ms
W
7
2 /f 3.91 ms
W
8
2 /f 7.81 ms
W
9
2 /f 15.6 ms
W
10
2 /f 31.3 ms
W
11
2 /f 62.5 ms
W
Remark f : Peripheral hardware clock frequency
PRS
f : Subsystem clock frequency
SUB
f : Watch timer clock frequency (f
W

10.2 Configuration of Watch Timer

The watch timer includes the following hardware.
Counter
Prescaler
Control register
288
CHAPTER 10 WATCH TIMER
Table 10-1. Watch Timer Interrupt Time
When Operated at
f = 2 MHz
PRS
1.02 ms
2.05 ms
0.52 s
1.05 s
7
/2 or f
PRS
Table 10-2. Interval Timer Interval Time
When Operated at
f = 2 MHz
PRS
1.02 ms
2.05 ms
4.10 ms
8.20 ms
16.4 ms
32.8 ms
65.5 ms
131.1 ms
7
/2 or f
PRS
Table 10-3. Watch Timer Configuration
Item
5 bits × 1
11 bits × 1
Watch timer operation mode register (WTM)
Preliminary User's Manual U17260EJ3V1UD
When Operated at When Operated at
f = 5 MHz f
PRS PRS
µ
410 s 205
µ
819 s 410
0.210 s 0.105 s
0.419 s 0.210 s
)
SUB
When Operated at When Operated at
f = 5 MHz f
PRS PRS
µ
410 s 205
µ
820 s 410
1.64 ms 820
3.28 ms 1.64 ms
6.55 ms 3.28 ms
13.1 ms 6.55 ms
26.2 ms 13.1 ms
52.4 ms 26.2 ms
)
SUB
Configuration
When Operated at
= 10 MHz f = 20 MHz
PRS
µ µ
s 102 s
µ µ
s 205 s
52.5 ms
0.105 s
When Operated at
= 10 MHz f = 20 MHz
PRS
µ µ
s 102 s
µ µ
s 205 s
µ µ
s 410 s
µ
820 s
1.64 ms
3.28 ms
6.55 ms
13.1 ms