CHAPTER 8 WATCH TIMER
171
User’s Manual U11302EJ4V0UM
Figure 8-2. Format of Timer Clock Select Register 2
Note
When using a main system clock of 1.25 MHz or less and the VFD controller/driver, select f
X
/2
8
as
the count clock for the watch timer.
Caution
When changing the count clock, be sure to stop operation of the watch timer before
rewriting TCL2 (stopping operation is not necessary when rewriting the same data).
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
×
0
0
1
1
TCL25
×
0
1
0
1
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