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2.3.4. Operations
Oscillation start time and oscillation stabilization waiting time
The oscillation start time refers to the time after the oscillator circuit is enabled until the oscillation
signal is actually sent to the internal circuits. The oscillation stabilization waiting time refers to the
time it takes the clock to stabilize after the oscillation starts. To avoid malfunctions of the internal
circuits due to an unstable clock during this period, the oscillator circuit includes an oscillation
stabilization waiting circuit that can disable sup- plying the clock to the system until the designated
time has elapsed. Figure 2.3.4.1 shows the relationship between the oscillation start time and the
oscillation stabilization waiting time.
System supply waiting time
Oscillation start time
Oscillator circuit enable
(∗OSC∗EN)
Oscillation waveform
Digitized oscillation waveform
Oscillator circuit output clock
(∗OSC∗CLK)
Oscillation stabilization waiting completion flag
(∗OSC∗STAIF)
Oscillation stabilization waiting time
Figure 2.3.4.1 Oscillation Start Time and Oscillation Stabilization Waiting Time
The oscillation stabilization waiting times for the OSC1 and OSC3 oscillator circuits can be set
using the CLGOSC1.OSC1WT[1:0] bits and CLGOSC3.OSC3WT[2:0] bits, respectively. To check
whether the oscillation stabilization waiting time is set properly and the clock is stabilized
immediately after the oscillation starts or not, monitor the oscillation clock using the FOUT output
function. The oscillation stabilization waiting time for the IOSC oscillator circuit is fixed at 16
IOSCCLK clocks. The oscillation stabilization waiting time for the OSC1 oscillator circuit should be set
to 16,384 OSC1CLK clocks or more when crystal oscillator is selected, or 4,096 OSC1CLK clocks or
more when internal oscillator is selected. The oscillation stabilization waiting time for the OSC3
oscillator circuit should be set to 1,024 OSC3CLK clocks or more.
When the oscillation stabilization waiting operation has completed, the oscillator circuit sets the
oscillation stabilization waiting completion flag and starts clock supply to the internal circuits.
Note:
The oscillation stabilization waiting time is always expended at start of oscillation even if the os-
cillation stabilization waiting completion flag has not be cleared to 0.
Seiko Epson Corporation
2-12
S1C31D50 TECHNICAL MANUAL
(Rev. 1.00)
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