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When the oscillation startup control circuit in the OSC1 oscillator circuit is enabled by setting the
CLGOSC1.OS- C1BUP bit to 1, it uses the high-gain oscillation inverter for a set period of time (startup
boosting operation) after the oscillator circuit is enabled (by setting the CLGOSC.OSC1EN bit to 1) to
reduce oscillation start time. Note, however, that the oscillation operation may become unstable if
there is a large gain differential between normal operation and startup boosting operation.
Furthermore, the oscillation start time being actually reduced depends on the characteristics of the
resonator used. Figure 2.3.4.2 shows an operation example when the oscillation start-up control circuit
is used.
(1) CLGOSC1.OSC1BUP bit = 0 (startup boosting operation disabled)
Oscillator circuit enable
Oscillation waveform
(2) CLGOSC1.OSC1BUP bit = 1 (startup boosting operation enabled)
Oscillator circuit enable
Oscillation waveform
Figure 2.3.4.2 Operation Example when the Oscillation Startup Control Circuit is Used
S1C31D50 TECHNICAL MANUAL
(Rev. 1.00)
(CLGOSC.OSC1EN)
Oscillation inverter
(CLGOSC.OSC1EN)
Oscillation inverter
INV1B[1:0] setting gain
Startup boosting
Seiko Epson Corporation
INV1N[1:0] setting gain
Normal operation
INV1N[1:0] setting gain
Normal operation
operation
2-13
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