| 摘要 |
PURPOSE:To attain phase margin check without using any exclusive test equipment by giving at any time a shift command to a phase shift circuit in a synchronizing signal separator circuit so as to give a synchronizing clock pulse whose phase is shifted by a prescribed quantity to a modulation conversion circuit thereby allowing the data conversion control circuit to detect the presence of read error of recording information. CONSTITUTION:A phase shift circuit 30 is provided to a synchronizing signal separator circuit 20 separating synchronizing information from a 1st modulation read signal and generating a synchronizing clock pulse train based thereupon. Then the modulation conversion circuit 10 converts the 1st modulation read signal into a 2nd modulation signal based on a synchronizing clock pulse while a shift command is given to the phase shift circuit 30 to give a prescribed phase difference between the 1st modulation read signal and the synchronizing clock pulse and a data conversion control circuit 40 converts the 2nd modulation read signal into a data signal to detect the presence of read error of the recording information based on the error detection information. Thus, the phase margin check is simply executed at any time without using any exclusive test equipment.
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