Apparatus for enabling PLL to lock on to a correct frequency and phase during the reproduction of a continuous-wave-corresponding signal and repetition of a specific pattern

1. A reproducing apparatus comprising:

first means for reproducing a signal representative of digital information from a recording medium;

second means for sampling the signal reproduced by the first means in response to a clock signal to generate a sampling-resultant signal;

third means for subjecting the sampling-resultant signal to a re-sampling process and an interpolation process responsive to timing information to generate a re-sampling-resultant signal;

fourth means for deciding whether the re-sampling-resultant signal is in a continuous-wave interval where an inversion period of the re-sampling-resultant signal remains constant or in a random-wave interval where the inversion period of the re-sampling-resultant signal varies at random;

fifth means for extracting a first value of the re-sampling-resultant signal at a time point corresponding to every zero-cross timing, for controlling a polarity of the extracted first value in response to whether the re-sampling-resultant signal is rising or falling in value to generate a polarity-control-resultant value, and for generating a first phase error in response to the polarity-control-resultant value;

sixth means for repetitively extracting a second value of the re-sampling-resultant signal at a constant period corresponding to a normal inversion period occurring during the continuous-wave interval, for alternately changing a polarity of the extracted second value between positive and negative to generate a polarity-change-resultant value, and for generating a second phase error in response to the polarity-change-resultant value;

seventh means for selecting the first phase error generated by the fifth means when the fourth means decides that the re-sampling-resultant signal is in a random-wave interval, and for selecting the second phase error generated by the sixth means when the fourth means decides that the re-sampling-resultant signal is in a continuous-wave interval;

a loop filter for integrating the phase error selected by the seventh means to generate a phase-error integration result; and

eighth means for generating the timing information in response to the phase-error integration result generated by the loop filter.

2. A reproducing apparatus as recited in claim 1 , wherein the fourth means comprises:

means for deciding whether or not a latest inversion period Y of the re-sampling-resultant signal satisfies one of relations as follows:

X− 1 ≦Y≦X+ 1

X− 2≦ Y≦X

X≦Y≦X+ 2

where X denotes the normal inversion period occurring in the continuous-wave interval;

means for deciding whether or not the latest inversion period Y consecutively satisfies one of the relations a prescribed number of times; and

means for deciding that the re-sampling-resultant signal is in a continuous-wave interval when the latest inversion period Y consecutively satisfies one of the relations the prescribed number of times.

3. A reproducing apparatus as recited in claim 1 , wherein the fourth means comprises:

means for detecting a latest period Z for which the re-sampling-resultant signal either rises or falls;

means for deciding whether or not the latest period Z satisfies one of relations as follows:

2 X− 1 ≦Z≦ 2 X+ 1

2 X− 2≦ Z≦ 2 X

2 X≦Z≦ 2 X+ 2

where X denotes the normal inversion period occurring in the continuous-wave interval;

means for deciding whether or not the latest period Z consecutively satisfies one of the relations a prescribed number of times; and

means for deciding that the re-sampling-resultant signal is in a continuous-wave interval when the latest period Z consecutively satisfies one of the relations the prescribed number of times.

4. A reproducing apparatus as recited in claim 1 , wherein the fourth means comprises:

means for deciding whether or not a latest inversion period of the re-sampling-resultant signal exceeds a preset period; and

means for controlling the seventh means to select the first phase error when it is decided that the latest inversion period of the re-sampling-resultant signal exceeds the preset period.

5. A reproducing apparatus as redited in claim 1 , wherein the third means, the fifth means, the sixth means, the seventh means, the loop filter, and the eighth means compose a feedback loop, and further comprising means for changing a loop gain of the feedback loop in response to which of the first phase error and the second phase error is selected by the seventh means.

6. A reproducing apparatus as redited in claim 1 , wherein the seventh means comprises:

means for measuring a time interval for which the second phase error remains selected; and

means for selecting the first phase error instead of the second phase error when the measured time interval reaches a predetermined time value.

7. A reproducing apparatus as recited in claim 1 , further comprising:

ninth means for recovering the digital information from the re-sampling-resultant signal;

tenth means for deciding whether or not a sync signal regularly appears in the recovered digital information; and

eleventh means for forcing the seventh means to select the first phase error when the tenth means decides that a sync signal regularly appears in the recovered digital information.