Overview Of Watch Prescaler - Fujitsu F2MC-8FX Hardware Manual

CHAPTER 13 WATCH PRESCALER
13.1

Overview of Watch Prescaler

The watch prescaler is a 15-bit down-counting, free-run counter, which is synchronized
with the subclock 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 as its count clock.
• The counter of the watch prescaler counts down and an interrupt request is generated every time the
selected interval time has elapsed.
• The interval time can be selected from the following four types:
Table 13.1-1 shows the interval times of the watch prescaler.
Table 13.1-1 Interval Times of Watch Prescaler
F : Subclock
CL
The values in parentheses represent the values achieved when the subclock operates at 32.768kHz.
Note:
The watch prescaler cannot be used in single system clock product.
192
Internal count clock cycle
μ
2/F (61.0 s)
CL
Interval time
11
2 x 2/F (125ms)
CL
12
2 x 2/F (250ms)
CL
13
2 x 2/F (500ms)
CL
14
2 x 2/F (1.00s)
CL