NEC 78K0 User Manual page 258
8-bit single-chip microcontrollers
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Figure 10-2. Format of Watch Timer Operation Mode Register (WTM)
Address: FF6FH
After reset: 00H
Symbol
7
WTM
WTM7
WTM7
0
1
WTM6
0
0
0
0
1
1
1
1
WTM3
0
0
1
1
WTM1
0
1
WTM0
0
1
Caution Do not change the count clock and interval time (by setting bits 4 to 7 (WTM4 to WTM7) of WTM)
during watch timer operation.
Remarks 1. f
: Watch timer clock frequency (f
W
2. f
: X1 input clock oscillation frequency
X
3. f
: Subsystem clock oscillation frequency
XT
4. Figures in parentheses apply to operation with f
258
CHAPTER 10 WATCH TIMER
R/W
6
5
WTM6
WTM5
WTM4
Watch timer count clock selection
7
f
/2
(78.125 kHz)
X
f
(32.768 kHz)
XT
WTM5
WTM4
4
0
0
2
/f
5
0
1
2
/f
6
1
0
2
/f
7
1
1
2
/f
8
0
0
2
/f
9
0
1
2
/f
10
1
0
2
/f
11
1
1
2
/f
WTM2
14
0
2
/f
W
13
1
2
/f
W
5
0
2
/f
W
4
1
2
/f
W
Clear after operation stop
Start
Operation stop (clear both prescaler and timer)
Operation enable
7
/2
X
User's Manual U15947EJ2V0UD
4
3
2
WTM3
WTM2
Prescaler interval time selection
W
W
W
W
W
W
W
W
Interrupt time selection
*
5-bit counter operation control
Watch timer operation enable
or f
)
XT
= 10 MHz, f
= 32.768 kHz.
X
XT
<1>
<0>
WTM1
WTM0
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