Rotation control apparatus, reproduction apparatus to which rotation control apparatus is applied, and rotation control method

摘要

A rotation control apparatus which does not rely upon a drop of a signal is provided. A lower limit frequency and an upper limit frequency calculated based on generation patterns of run length limited codes which may possibly be generated stochastically are set as a frequency variation range. When rotation control is performed based on an error between a frequency of run length limited codes reproduced from a disk and a reference frequency while a PLL circuit is not in a locked condition, the reference frequency is varied between the upper limit frequency and the lower limit frequency. Then, the reference frequency which is currently used for comparison when the PLL circuit is put into a locked condition is stored as a fixed value and used as the reference frequency for later rotation control.