196
CHAPTER 9 WATCH TIMER
User
’
s Manual U14701EJ3V0UD
Figure 9-2. Watch Timer Operation Mode Register 0 (WTNM0) Format
Address: FF41H After reset: 00H R/W
Symbol
7
6
5
4
3
2
1
0
WTNM0
WTNM07
WTNM06
WTNM05
WTNM04
WTNM03
WTNM02
WTNM01
WTNM00
WTNM07
Watch timer count clock selection
0
f
X
/2
8
(39.1 kHz)
1
f
XT
(32.768 kHz)
WTNM06
WTNM05
WTNM04
11-bit prescaler interval time selection
WTNM07 = 0
WTNM07 = 1
0
0
0
2
4
/f
W
2
12
/f
X
(409.6
μ
s)
2
4
/f
XT
(488
μ
s)
0
0
1
2
5
/f
W
2
13
/f
X
(819.2
μ
s)
2
5
/f
XT
(977
μ
s)
0
1
0
2
6
/f
W
2
14
/f
X
(1.64 ms)
2
6
/f
XT
(1.95 ms)
0
1
1
2
7
/f
W
2
15
/f
X
(3.28 ms)
2
7
/f
XT
(3.91 ms)
1
0
0
2
8
/f
W
2
16
/f
X
(6.56 ms)
2
8
/f
XT
(7.81 ms)
1
0
1
2
9
/f
W
2
17
/f
X
(13.1 ms)
2
9
/f
XT
(15.6 ms)
1
1
0
2
10
/f
W
2
18
/f
X
(26.2 ms)
2
10
/f
XT
(31.2 ms)
1
1
1
2
11
/f
W
2
19
/f
X
(52.4 ms)
2
11
/f
XT
(62.4 ms)
WTNM03
WTNM02
Selection of interrupt request time of the watch timer
WTNM07 = 0
WTNM07 = 1
0
0
2
14
/f
W
2
22
/f
X
(0.41 s)
2
14
/f
XT
(0.5 s)
0
1
2
13
/f
W
2
21
/f
X
(0.2 s)
2
13
/f
XT
(0.25 s)
1
0
2
5
/f
W
2
13
/f
X
(819.2
μ
s)
2
5
/f
XT
(977
μ
s)
1
1
2
4
/f
W
2
12
/f
X
(409.6
μ
s)
2
6
/f
XT
(488
μ
s)
WTNM01
5-bit counter operation control
0
Clear after operation stop
1
Start
WTNM00
Watch timer operation enable
0
Operation stop (clear both 11-bit prescaler and 5-bit counter)
1
Operation enable
Caution Do not change the count clock, interval time, and interrupt request time (by using bits 2 to 7
(WTNM02 to WTNM07) of WTNM0) while the watch timer is operating.
Remarks 1.
f
W
: Watch timer clock frequency (f
X
/2
8
or f
XT
)
f
X
:
Main system clock oscillation frequency
f
XT
: Subsystem clock oscillation frequency
2.
Figures in parentheses apply to operation with f
X
= 10 MHz, f
XT
= 32.768 kHz.