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CHAPTER 3 CPU
3.6.5
Oscillation Stabilization Wait Time
Oscillation stabilization wait time is to be applied when power is turned on to start the
clock in RUN mode while the clock is stopped in stop mode.
s Oscillation Stabilization Wait Time
A ceramic or crystal resonator normally requires several or several tens of milli-seconds from
oscillation start to oscillation stabilization at a specific cycle (oscillation frequency).
Thus, CPU operation must be prohibited immediately after the start of oscillation, and the clock
is to be supplied to the CPU when oscillation is stable following the expiration of oscillation
stabilization wait time.
The period during which oscillation becomes stable is dependent on the type of oscillator (such
as crystal or ceramic) connected to the oscillation circuit (clock generator).
Therefore, an
oscillation stabilization wait time setting appropriate to the oscillator used must be selected.
Figure 3.6-6 "Changes of a Frequency after Generation" shows changes in a frequency
generated by an oscillator from generation to stabilization.
Figure 3.6-6 Changes of a Frequency after Generation
s Oscillation Stabilization Wait Time
Oscillation stabilization wait time is to be applied to start the clock in active mode while the clock
is stopped.
Oscillation stabilization wait time is the duration from when the counter of the time base timer is
cleared to when the specified bits overflow.
r Oscillation stabilization wait time during operation
For oscillation stabilization wait time applied for a return from stop mode to active (RUN) mode
due to external interrupt, one of three oscillation stabilization wait time settings can be selected
using the oscillation stabilization wait time selection bits in the system clock control register
(SYCC: WT1 and WT0).
r Oscillation stabilization wait time at a reset
Option settings specify oscillation stabilization wait time at a reset (initial values of WT1 and
X1
Duration required for a resonator
starts oscillation
Oscillation
stabilization wait time
Normal operation
Return from stop mode
or reset operation
Start of oscillation
Oscillation stabilizes