FUJITSU Semiconductor Controller MB89950/950A - Manual (Page 80)

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CHAPTER 3 CPU
■ Oscillation stabilization delay time
As the oscillator that provides the oscillation source is stopped during stop mode, a delay time is required
for oscillation to stabilize after the oscillator restarts operation.
In main clock mode, the main clock oscillation stabilization delay time is selected from one of two possible
delay times defined by the timebase timer.
In main clock mode, if the interval time set for the timebase timer is less than the oscillation stabilization
delay time, the timebase timer generates an interval timer interrupt request before the end of the oscillation
stabilization delay time. To prevent this, disable the interrupt request output for the timebase timer (TBTC:
TBIE = "0") before going to stop mode in main clock mode as necessary.