Overview - Fujitsu 8FX Hardware Manual

CHAPTER 9 WATCH PRESCALER

9.1 Overview

9.1 Overview
The watch prescaler is a 16-bit down-counting, free-run counter, which is
synchronized with the subclock divided by two or the sub-CR clock divided by
two. It has an interval timer function that continuously generates interrupt
requests at regular intervals.
■ Interval Timer Function
The interval timer function continuously generates interrupt requests at regular intervals, using
the subclock divided by two or the sub-CR clock divided by two as its count clock.
• The counter of the watch prescaler counts down and an interrupt request is generated
whenever the selected interval time has elapsed.
• The interval time can be selected from the following eight types:
Table 9.1-1 shows the interval times of the watch prescaler.
Table 9.1-1
n=10
n=11
n=12
n=13
n=14
n=15
n=16
n=17
*1: 2/F
*2: 2/F
Note:
Refer to the device data sheet for the accuracy of the sub-CR clock frequency.
112
Interval Times of Watch Prescaler
Interval time
(Sub-CR clock)
n *1
(2 2/F
CRL
20.48 ms
40.96 ms
81.92 ms
163.84 ms
327.68 ms
655.36 ms
1.311 s
2.621 s
=20 µs when F =100 kHz
CRL CRL
=61.035 µs when F =32.768 kHz
CL CL
FUJITSU SEMICONDUCTOR LIMITED
Interval time
(Subclock)
n *2
) (2 2/F )
CL
62.5 ms
125 ms
250 ms
500 ms
1 s
2 s
4 s
8 s
MB95630H Series
MN702-00009-2v0-E