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CHAPTER 11 TIMEBASE TIMER
11.5 Explanation of Operations of Timebase Timer Functions
The timebase timer operates as an interval timer or an oscillation stabilization wait time
timer. It also supplies a clock to peripherals.
■ Interval Timer Function
Interrupt generation at every interval time enables the timebase timer to be used as an interval timer.
Operating the timebase timer as an interval timer requires the settings shown in Figure 11.5-1 .
●
Setting of timebase timer
Figure 11.5-1 Setting of Timebase Timer
●
Operations of the Interval Timer Functions
The timebase timer can be used as an interval timer by generating an interrupt at every set interval time.
• The timebase timer continues incrementing in synchronization with the main clock (a half
frequency of the oscillation clock) while the oscillation clock is active.
• When the timebase timer counter reaches the interval time set by the interval time select bits
in the timebase timer control register (TBTC: TBC1, TBC0), it causes an overflow (carrying)
and the overflow interrupt request flag bit (TBTC: TBOF) is set to "1".
• When the overflow interrupt request flag bit is set (TBTC: TBOF = 1) with interrupts enabled
(TBTC: TBIE = 1), an interrupt request is generated.
Note:
The interval time may be longer than the one set by clearing the timebase timer counter.
●
Example of operation for timebase timer
Figure 11.5-2 gives an example of the operation that the timebase timer performs under the following
conditions:
• A power-on reset occurs.
• The mode transits to the sleep mode during the operation of the interval timer.
• The mode transits to the stop mode during the operation of the interval timer.
• A request to clear the timebase timer counter is issued.
TBIE TBOF TBC1
TBC0
TBR
001
bit15 14 13 12 11 10
9 bit8
0
1
: Undefined bit
: Used bit
: Set to "0".
: Set to "1".
Timebase timer control register
(TBTC)
Re-
served