Overview Of Watch Timer - Fujitsu F2MCTM-16LX Hardware Manual

CHAPTER 15 WATCH TIMER
15.1

Overview of Watch Timer

The watch timer is a 15-bit free-run counter that increments in synchronization with the
subclock.
• Eight interval times can be selected and an interrupt request can be generated for
each interval time.
• An operation clock can be supplied to the oscillation stabilization wait time timer of
the subclock and the watchdog timer.
• The subclock is always used as a count clock regardless of the settings of the clock
select register (CKSCR).
Interval Timer Function
• When the watch timer reaches the interval time set by the interval time select bits (WTC:WTC2 to
WTC0), the bit corresponding to the interval time of the watch timer counter overflows (carries) and the
overflow flag bit is set (WTC:WTOF = 1).
• When the overflow flag bit is set (WTC:WTOF = 1) with interrupt enabled when an overflow occurs
(WTC:WTIE = 1), an interrupt request is generated.
• The interval time of the watch timer can be selected from eight types shown in Table 15.1-1 .
Table 15.1-1 Interval Times of Watch Timer
SCLK: Subclock frequency
The parenthesized values are provided when the subclock operates at 8.192 kHz. Please consider the frequency
difference of built-in CR oscillation when you use built-in CR oscillation clock as a sub-clock.
268
Subclock Cycle
SCLK(122 µs)
Interval Time
8
2 /SCLK(31.25 ms)
9
2 /SCLK(62.5 ms)
10
2 /SCLK(125 ms)
11
2 /SCLK(250 ms)
12
2 /SCLK(500 ms)
13
2 /SCLK(1.0 s)
14
2 /SCLK(2.0 s)
15
2 /SCLK(4.0 s)