Oscillation Stabilization Delay Time; Figure 3.6-6 Operation Of An Oscillator After Starting Oscillation - Fujitsu F2MC-8L Series Hardware Manual

3.6.5

Oscillation Stabilization Delay Time

As the main clock remains stopped before the power is turned on, during main stop
mode or subclock mode, a main clock oscillation stabilization delay time is required to
enter the main-RUN operation mode. Similarly, in subclock mode, a subclock
oscillation stabilization delay time is required since the subclock oscillation is
stopped.
Oscillation Stabilization Delay 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 is disabled when oscillation first starts and no clock signal is
supplied to the CPU until the oscillation stabilization delay 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 oscillator (clock generator). Consequently, it is necessary to select an
oscillation stabilization delay time that matches the type of oscillator being used.
Figure 3.6-6 shows the operation of an oscillator immediately after starting oscillation.

Figure 3.6-6 Operation of an Oscillator after Starting Oscillation

X1
Oscillation starts
Main Clock Oscillation Stabilization Delay Time
Before restarting operation in main clock mode with the main clock stopping oscillation, the CPU
must take the main clock oscillation stabilization delay time.
The main clock oscillation stabilization delay time is the time from when the timebase timer/
counter starts incrementing from the cleared state until an overflow occurs on the specified bit.
Oscillation stabilization delay time during operation
The oscillation stabilization delay time required for the CPU to return to main-RUN mode from
main-stop mode in response to an external interrupt or to main clock mode from subclock mode
can be selected from four types depending on the settings of the oscillation stabilization delay
time select bits (WT1 and WT0) in the system clock control register (SYCC).
Oscillation stabilization
Resonator oscillation time delay time
Oscillation stabilizes
Normal operation
(wake-up from stop mode
or reset operation)
3.6 Clocks
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