Operations Of Time-Base Timer - Fujitsu MB90390 Series Hardware Manual

11.3

Operations of Time-base Timer

The time-base timer functions as a watch-dog timer clock source, timer for oscillation
stabilization wait time, and interval timer for generating interrupts at specified intervals.
■ Time-base Counter
The time-base counter consists of an 18-bit counter for a clock generated by dividing the source oscillation
input by two. This clock is used to generate the machine clock. While the source oscillation is input, the
time-base counter keeps counting. The time-base counter is cleared by a power-on reset, transition to stop
or writing "0" to the TBR bit of the TBTC register.
■ Interval Interrupt Function
Interrupts are generated at specified intervals according to the carry signals of the time-base counter. The
TBOF flag is set at the intervals specified with the TBC1 and TBC0 bits of the TBTC register. The flag is
written to reference to the time at which the time-base timer is cleared last.
Upon transition to stop mode, the time-base timer is used as a timer for oscillation stabilization wait time
upon recovery. Therefore, the TBOF flag is immediately cleared upon mode transition.
CHAPTER 11 TIME-BASE TIMER
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