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CHAPTER 9 TIMEBASE TIMER
MB90560 series
9.5
Operation of the Timebase Timer
The timebase timer provides the interval timer function and the clock supply function
that supplies clocks to some peripheral functions.
I
Operation of the interval timer function (timebase timer)
The interval timer function generates an interrupt request for each interval
The setting in Figure 9.5-1 is required for timebase timer to operate as an interval timer.
Figure 9.5-1 Setting of the timebase timer
The timebase timer counter continues counting up in synchronization with the internal count
clock (one-half of the oscillation clock) as long as the clock is being oscillated.
When the counter is cleared (TBR = 0), it counts up from “0”. When the interval timer bit
overflows, the interrupt request flag bit (TBOF) is set to “1”. If interrupt request output has
been enabled (TBIE = 1), an interrupt is generated for each selected interval based on the
cleared time.
The interval may become longer than the time set because of timebase timer clearing.
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Oscillation stabilization wait interval timer function
The timebase timer is also used as the oscillation stabilization wait interval timer for oscillation
and the PLL clocks.
The oscillation settling time is set for the interval from the time the counter counts up from “0”
(count clear) until the oscillation stabilization wait interval bit overflows. When control returns
from timebase timer mode to PLL clock mode, the oscillation stabilization wait interval starts from
the middle of counting because the timebase timer counter has been not cleared. Table 9.5-1
shows the clearing of the timebase counter and the oscillation settling times.
: Used
: Set "0"
: Set "1"