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Chapter 10
Watch Timer
Preliminary User’s Manual U14913EE1V0UM00
(1)
Watch timer
The watch timer generates an interrupt request (INTWT) at time intervals of 512 µs or 2.097 s by
using the subsystem clock f
CKSEL1
or f
CKSEL2
or the derived 11-bit prescaler clock from f
CKSEL1
or
f
CKSEL2
(refer to Figure 8-1: “Block Diagram of the Clock Generator” on page 225).
(2)
Interval timer
The interval timer generates an interrupt request (INTWTI) at time intervals specified in advance.
Table 10-1: Interval Time of Interval Timer (f
SUB
= 4 MHz)
Remarks: 1. fw: Watch timer clock frequency
2. interval times change accordingly if f
SUB
= 5 MHz
10.2 Configuration
The watch timer consists of the following hardware:
Table 10-2: Configuration of Watch Timer
Interval Time
fw =
f
CKSEL2
fw =
f
CKSEL1
2
4
× 1/f
W
2.408 ms
512 µs
2
5
× 1/f
W
4.096 ms
1.024 ms
2
6
× 1/f
W
8.192 ms
2.048 ms
2
7
× 1/f
W
16.384 ms
4.096 ms
2
8
× 1/f
W
32.768 ms
8.192 ms
2
9
× 1/f
W
65.536 ms
16.384 ms
2
10
× 1/f
W
131.072 ms
32.768 ms
2
11
× 1/f
W
262.144 ms
65.536 ms
Item
Configuration
Counter
5 bits × 1
Prescaler
11 bits × 1
Control register
Watch timer mode control register (WTM)
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