Figure 5.5A Interval Timer Function Settings - Fujitsu F2MC-8L MB89620 Series Hardware Manual

5
5. Operation of Timebase Timer
The timebase timer has the interval timer function and the clock supply function for
some peripherals.
n Operation of Interval Timer Function (Timebase Timer)
Figure 5.5a shows the settings required to operate the interval timer function.
Provided the clock is oscillating, the timebase timer counter continues to count-up in sync with
the internal count clock (divide-by-two source oscillation).
After being cleared (TBR = "0"), the counter restarts counting-up from zero. The timebase timer
sets the overflow interrupt request flag bit (TBOF) to "1" when an overflow occurs on the interval
timer bit. Consequently, the timebase timer generates interrupt requests at fixed intervals (the
selected interval time), based on the time that the counter is cleared.
n Operation of Clock Supply Function
The timebase timer is also used as a timer to generate the oscillation stabilization delay time.
The timebase timer counter is cleared when the device changes to stop mode (STBC: STP =
"1") or when a power-on reset (optional) occurs. The time from when the counter starts counting-
up from zero until an overflow occurs on the oscillation stabilization delay time bit is the
oscillation stabilization delay time. The oscillation stabilization delay time bit can be set
(optional) to one of two bits (for crystal or ceramic resonators respectively).
The timebase timer also provides the clock for the watchdog timer and buzzer output. Clearing
the timebase timer counter simultaneously clears the watchdog timer counter. This also affects
the operation of the continuous activation cycle of the A/D converter and the buzzer output.
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CHAPTER 5 TIMEBASE TIMER
Bit 7 Bit 6 Bit 5
TBTC — —

Figure 5.5a Interval Timer Function Settings

Bit 4 Bit 3 Bit 2
— TBIE TBOF TBR
1 0 0
Bit 1 Bit 0
TBC1 TBC0
: Used bit
1 : Set "1".
0 : Set "0".
MB89620 series