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CHAPTER 3 CPU
3.6.5
Oscillation Stabilization Wait Time
When the system transitions to main-run mode from a state in which the main clock is
stopped (such as at power-on, and in main-stop and subclock modes, etc.), a wait time
is required for oscillation to stabilize before operation starts.
Similarly, a subclock oscillation stabilization wait time is required when exiting the sub-
stop mode, because the subclock oscillator is stopped in that mode.
I Oscillation stabilization wait time
After starting, ceramic, crystal, and other resonators typically require the time between several milliseconds
and several tens of milliseconds to stabilize at their fixed oscillation frequency.
Therefore, operation of the CPU and other functions is disabled when oscillation first starts and no clock
signal is supplied to the CPU and peripheral functions until the oscillation stabilization wait time has
passed and the oscillation has sufficiently stabilized.
The time required for oscillation to stabilize depends on the resonator type (crystal, ceramic, etc.)
connected to the clock generator. Consequently, it is necessary to select an oscillation stabilization wait
time that matches the type of oscillator being used.
Figure 3.6-6 "Operation of oscillator after starting oscillation" shows the operation of an oscillator after
starting oscillation.
Figure 3.6-6 Operation of oscillator after starting oscillation
I Regulator recovery time
MB89470 series contains an on-chip voltage regulator for the internal 3 V circuits. In power-down mode or
in the stop mode, the internal voltage regulator is turned off to minimize power consumption. The
Regulator Recovery Time is the the time for the internal voltage regulator to resume normal operation.
The Regulator Recovery Time is 20
second long, and it is required only in MB89P475.
I Power-on stabilization time
When power-on, the on-chip voltage regulator requires a stabilization time in addition to the oscillation
stabilization time. This additional wait time is called Power-On Stabilization Time. The external power
supply voltage must reach the mininum operation voltage within the Power-On stabilization time.
The Power-On Stabilization Time is required in MB89P475 and MB89475. It depends on the oscillating
clock, and it is 217/ FCH long (FCH is the main clock operating frequency).
Resonator oscillation time Oscillation stabilization wait time
Oscillation starts
Oscillation stabilizes
Normal operation
(wake-up from stop mode,
subclock mode
or reset operation)