Oscillation Stabilization Wait Time - Fujitsu F2MC-8FX Hardware Manual

CHAPTER 6 CLOCK CONTROLLER
6.2

Oscillation Stabilization Wait Time

The oscillation stabilization wait time is the time after the oscillator circuit stops
oscillation until the oscillator resumes its stable oscillation at its natural frequency. The
clock controller obtains the oscillation stabilization wait time by counting a set number
of oscillation clock cycles to prevent clock supply to internal circuits.
Oscillation Stabilization Wait Time
The clock controller obtains the oscillation stabilization wait time followed by the initiation of oscillation
by counting a set number of oscillation clock cycles to prevent clock supply to internal circuits.
When a state transition request for starting oscillation when the power is turned on or for restarting halted
oscillation at a clock mode change by a reset, an interrupt in standby mode, or by software, the clock
controller automatically waits until the oscillation stabilization wait time for the main clock or subclock has
passed and then causes transition to the next state.
Figure 6.2-1 shows oscillation immediately after being started.
Figure 6.2-1 Behavior of Oscillator Immediately after Starting Oscillation
The main clock oscillation stabilization wait time is counted by using the timebase timer. The subclock
oscillation stabilization wait time is counted by using the watch prescaler. The count can be set in the
oscillation stabilization wait time setting register (WATR). Set it in keeping with the oscillator
characteristics.
When a power-on reset occurs, the oscillation stabilization wait time is fixed to the initial value.
Table 6.2-1 shows the length of oscillation stabilization wait time.
Table 6.2-1 Oscillation Stabilization Wait Time
Clock
Main clock
Subclock
(Two-system clock product)
After the oscillation stabilization wait time of the main clock ends, the oscillation stabilization wait time of
subclock measurement is begun.
PLL Clock Oscillation Stabilization Wait Time
As with the oscillation stabilization wait time of the oscillator, the clock controller automatically waits for
50
Oscillation time of
oscillator
X1
Oscillation started
Factor
Power-on reset
Other than power-on reset
Power-on reset
Other than power-on reset
Normal operation
(
Operation after returning
Oscillation stabilization
from stop mode or a reset
wait time
Oscillation stabilized
Oscillation Stabilization Wait Time
14
Initial value: (2 -2)/F , where F
CH
(specified when ROM is ordered for mask products)
Register setting value (WATR:MWT3, MWT2, MWT1, MWT0)
15
Initial value: (2 -2)/F , where F
CL
Register setting value (WATR:SWT3, SWT2, SWT1, SWT0)
)
is the main clock frequency
CH
is the subclock frequency.
CL