UPD78F0138 NEC, UPD78F0138 Datasheet - Page 230

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

9.1 Functions of Watch Timer
230
The watch timer has the following functions.
• Watch timer
• Interval timer
The watch timer and the interval timer can be used simultaneously.
Figure 9-1 shows the watch timer block diagram.
Remark
f
X
/2
f
XT
7
f
f
f
f
X
XT
W
WX
: X1 input clock oscillation frequency
: Watch timer clock frequency
: Subsystem clock oscillation frequency
: f
f
W
W
or f
f
W
/2
W
4
/2
f
W
9
/2
11-bit prescaler
5
f
W
/2
Figure 9-1. Block Diagram of Watch Timer
6
f
WTM7
W
/2
7
CHAPTER 9 WATCH TIMER
Clear
f
W
/2
8
User’s Manual U16228EJ2V0UD
WTM6
f
W
/2
10
f
W
Internal bus
/2
11
f
WTM5
W
/2
9
WTM4
f
WX
5-bit counter
WTM3
Watch timer operation
mode register (WTM)
Clear
WTM2
f
f
WX
WX
WTM1
/2
/2
4
5
WTM0
INTWT
INTWTI