NEC 78K0 User Manual page 205

Figure 9-2. Format of Watch Timer Operation Mode Register (WTM)
Address: FF6FH After reset: 00H
Symbol 7
WTM WTM7
WTM7
0 f
X
1 f
XT
WTM6
0
0
0
0
1
1
1
1
WTM3
0
0
1
1
WTM1
0 Clear after operation stop
1 Start
WTM0
0 Operation stop (clear both prescaler and timer)
1 Operation enable
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
CHAPTER 9 WATCH TIMER
R/W
6 5
WTM6 WTM5 WTM4
Watch timer count clock selection
7
/2 (78.125 kHz)
(32.768 kHz)
WTM5 WTM4
4
0 0 2 /f
W
5
0 1 2 /f
W
6
1 0 2 /f
W
7
1 1 2 /f
W
8
0 0 2 /f
W
9
0 1 2 /f
W
10
1 0 2 /f
W
11
1 1 2 /f
W
WTM2
14
0 2 /f
W
13
1 2 /f
W
5
0 2 /f
W
4
1 2 /f
W
5-bit counter operation control
7
/2 or f
X
User's Manual U16227EJ2V0UD
4 3 2
WTM3 WTM2
Prescaler interval time selection
Interrupt time selection
Watch timer operation enable
)
XT
= 10 MHz, f = 32.768 kHz.
X XT
<1> <0>
WTM1 WTM0
205