FUJITSU Semiconductor Controller MB89950/950A - Manual (Page 114)

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CHAPTER 5 TIMEBASE TIMER
5.1 Overview of Timebase Timer
The timebase timer provides interval timer functions. Four different interval times can
be selected. The timebase timer uses a 20-bit free-run counter which counts up in
synchronous with the internal count clock (divide-by-two the main clock oscillation
frequency). The timebase timer also provides the timer output for the oscillation
stabilization delay time, the operating clock for the watchdog timer, the operating clock
for LCD controller/driver and sampling clock for noise filter circuit in PWC timer.
The timebase timer stops operating in stop mode.
■ Interval timer function
The interval timer function generates repeated interrupts at fixed time intervals.
• The timer generates an interrupt each time the interval timer bit overflows on the timebase timer
counter.
• The interval timer bit (interval time) can be selected from four different settings.
Table 5.1-1 "Timebase timer interval time" lists the available interval time for the timebase timer.
Table 5.1-1 Timebase timer interval time
Internal count clock cycle Interval time (F
CH
= 5 MHz)
2/F
CH
2
15
/F
CH
(approx. 6.55 ms)
2
17
/F
CH
(approx. 26.21 ms)
2
19
/F
CH
(approx. 104.86 ms)
2
21
/F
CH
(approx. 419.43 ms)
F
CH
: Main clock oscillation frequency