UPD78F0138 NEC, UPD78F0138 Datasheet - Page 233

• Manufacturer Part Number: UPD78F0138
• Description: (UPD78xxxx) 8-Bit Single-Chip Microcontrollers
• Manufacturer: NEC

Caution Do not change the count clock and interval time (by setting bits 4 to 7 (WTM4 to WTM7) of WTM)
Remarks 1. f
Address: FF6FH
Symbol
WTM
during watch timer operation.
2. f
3. f
4. Figures in parentheses apply to operation with f
W
X
XT
WTM7
WTM7
WTM6
WTM3
WTM1
WTM0
: X1 input clock oscillation frequency
: Watch timer clock frequency (f
: Subsystem clock oscillation frequency
7
0
1
0
0
0
0
1
1
1
1
0
0
1
1
0
1
0
1
Figure 9-2. Format of Watch Timer Operation Mode Register (WTM)
After reset: 00H
f
f
Clear after operation stop
Start
Operation stop (clear both prescaler and timer)
Operation enable
X
XT
/2
WTM6
WTM5
WTM2
(32.768 kHz)
7
(78.125 kHz)
6
0
0
1
1
0
0
1
1
0
1
0
1
R/W
2
2
2
2
14
13
5
4
/f
/f
WTM5
WTM4
/f
/f
CHAPTER 9 WATCH TIMER
W
W
W
W
User’s Manual U16228EJ2V0UD
5
0
1
0
1
0
1
0
1
X
2
2
2
2
2
2
2
2
/2
4
5
6
7
8
9
10
11
/f
/f
/f
/f
/f
/f
7
WTM4
Watch timer count clock selection
/f
/f
W
W
W
W
W
W
or f
W
W
5-bit counter operation control
Watch timer operation enable
4
XT
)
X
Interrupt time selection
= 10 MHz, f
WTM3
Prescaler interval time selection
3
XT
WTM2
= 32.768 kHz.
2
WTM1
<1>
WTM0
<0>
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