Chapter 10 Watch Timer; Functions Of Watch Timer - NEC 78K0 User Manual

10.1 Functions of Watch Timer

The watch timer has the following functions.
• Watch timer
• Interval timer
The watch timer and the interval timer can be used simultaneously.
Figure 10-1 shows the watch timer block diagram.
7
f /2
X
f
W
f /2
f
W
XT
Remark f : X1 input clock oscillation frequency
X
f : Subsystem clock oscillation frequency
XT
f : Watch timer clock frequency
W
f : f or f
WX W W

CHAPTER 10 WATCH TIMER

Figure 10-1. Watch Timer Block Diagram
Clear
11-bit prescaler
4 5 6 7 8 10
f /2 f /2 f /2 f /2 f /2 f /2
W W W W W W
WTM7 WTM6
Internal bus
9
/2
User's Manual U15947EJ2V0UD
f
WX
5-bit counter
Clear
11 9
f /2
W
*
WTM5 WTM4 WTM3
Watch timer operation
mode register (WTM)
4
f /2
WX
5
f /2
INTWT
WX
INTWTI
WTM2 WTM1 WTM0
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