MB95630H Series
112 FUJITSU SEMICONDUCTOR LIMITED MN702-00009-2v0-E
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.
*1: 2/F
CRL
=20 µs when F
CRL
=100 kHz
*2: 2/F
CL
=61.035 µs when F
CL
=32.768 kHz
Note:
Refer to the device data sheet for the accuracy of the sub-CR clock frequency.
Table 9.1-1 Interval Times of Watch Prescaler
Interval time
(Sub-CR clock)
(2
n
× 2/F
CRL
*1
)
Interval time
(Subclock)
(2
n
× 2/F
CL
*2
)
n=10 20.48 ms 62.5 ms
n=11 40.96 ms 125 ms
n=12 81.92 ms 250 ms
n=13 163.84 ms 500 ms
n=14 327.68 ms 1 s
n=15 655.36 ms 2 s
n=16 1.311 s 4 s
n=17 2.621 s 8 s
To Next Page
Loading...
