135
CHAPTER 10 WATCH TIMER
10.3 Watch Timer Control Register
The watch timer mode control register (WTM) is used to control the watch timer.
• Watch timer mode control register (WTM)
This register sets the watch timer count clock, operation enable/disable, prescaler interval time and 5-bit counter
operation control.
WTM is set with an 8-bit memory manipulation instruction.
RESET input clears WTM to 00H.
Figure 10-2. Watch Timer Mode Control Register (WTM) Format
Address: FF41H After Reset: 00H R/W
Symbol
7
6
5
4
3
2
1
0
WTM
WTM7
WTM6
WTM5
WTM4
WTM3
0
WTM1
WTM0
WTM7
Watch Timer Count Clock Selection
0
f
X
/2
7
(65.4 kHz)
1
f
X
/2
11
(4.09 kHz)
WTM6
WTM5
WTM4
Prescaler Interval Time Selection
0
0
0
2
4
/f
W
(3.91 ms)
0
0
1
2
5
/f
W
(7.82 ms)
0
1
0
2
6
/f
W
(15.6 ms)
0
1
1
2
7
/f
W
(31.2 ms)
1
0
0
2
8
/f
W
(62.5 ms)
1
0
1
2
9
/f
W
(125 ms)
Other than above
Setting prohibited
WTM3
Watch Flag Set Time Selection
0
Normal operating mode (flag set at f
W
/2
14
)
1
Fast feed operating mode (flag set at f
W
/2
5
)
WTM1
5-bit Counter Operation Control
0
Clear after operation stop
1
Start
WTM0
Watch Timer Operation Control
0
Operation stop (clear both prescaler and timer)
1
Operation enable
Remarks 1. f
W
: Watch timer clock frequency (f
X
/2
7
or f
X
/2
11
)
2. f
X
: Main system clock oscillation frequency
3. Figures in parentheses apply to operation with f
X
= 8.38 MHz, f
W
= 4.09 kHz.
Содержание mPD780973 Series
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