CHAPTER 9 WATCHDOG TIMER
178
User’s Manual U11302EJ4V0UM
Figure 9-2. Format of Timer Clock Select Register 2
Note
f
X
/2
8
must be selected as the watch timer count clock when using a main system clock of 1.25 MHz
or less and the VFD controller/driver.
Caution
Changing the count clock (rewriting TCL20 to TCL22) after watchdog timer operation has
started is prohibited.
Remarks 1.
f
X
: Main system clock oscillation frequency
2.
f
XT
: Subsystem clock oscillation frequency
3.
x:
don’t care
4.
Figures in parentheses apply to operation with f
X
= 5.0 MHz or f
XT
= 32.768 kHz.
TCL20
TCL2
7
6
5
4
3
2
Symbol
1
0
TCL22
Count clock selection
FF42H
TCL21
0
TCL22
TCL24
TCL25
TCL26
TCL27
Address
After reset
R/W
00H
R/W
Watchdog timer mode
0
f
X
/2
3
(625 kHz)
0
f
X
/2
4
(313 kHz)
0
f
X
/2
5
(156 kHz)
0
f
X
/2
6
(78.1 kHz)
1
f
X
/2
7
(39.1 kHz)
1
f
X
/2
8
(19.5 kHz)
1
f
X
/2
9
(9.8 kHz)
1
f
X
/2
11
(2.4 kHz)
TCL24 Watch timer count clock selection
Note
0
f
X
/2
8
(19.5 kHz)
1
f
XT
(32.768 kHz)
TCL27
Buzzer output frequency selection
0
Buzzer output disabled
1
f
X
/2
10
(4.9 kHz)
1
f
X
/2
11
(2.4 kHz)
1
f
X
/2
12
(1.2 kHz)
1
Setting prohibited
Interval timer mode
f
X
/2
4
(313 kHz)
f
X
/2
5
(156 kHz)
f
X
/2
6
(78.1 kHz)
f
X
/2
7
(39.1 kHz)
f
X
/2
8
(19.5 kHz)
f
X
/2
9
(9.8 kHz)
f
X
/2
10
(4.9 kHz)
f
X
/2
12
(1.2 kHz)
TCL21
0
0
1
1
0
0
1
1
TCL20
0
1
0
1
0
1
0
1
TCL26
x
0
0
1
1
TCL25
x
0
1
0
1
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