Table of Contents
Advertisement
CHAPTER 9 Watch timer
9.1
Overview of Watch Timer
The watch timer is a 15-bit free-run counter that increments in synchronization with the
sub clock.
• Seven 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 sub clock and the watchdog timer.
• The sub clock is always used as a count clock regardless of the settings of the clock
select register (CKSCR).
I 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 seven types. The interval time of the watch
timer can be selected from seven types shown in Table 9.1-1.
Table 9.1-1 Interval Times of Watch Timer
SCLK: Sub clock frequency
The parenthesized values are provided when the sub clock operates at 8.192 kHz.
278
Sub clock Cycle
SCLK (122µs)
Interval Time
8
2
/SCLK (31.25ms)
9
2
/SCLK (62.5ms)
10
2
/SCLK (125ms)
11
2
/SCLK (250ms)
12
2
/SCLK (500ms)
13
2
/SCLK (1.0s)
14
2
/SCLK (2.0s)
15
2
/SCLK (4.0s)
Advertisement
Table of Contents
