| 摘要 |
<P>PROBLEM TO BE SOLVED: To attain the pull-in of a PLL by evading a read error even though a data period on a magnetic tape is narrowed, etc., due to the read of a mag netic tape drive. <P>SOLUTION: The PLL is constituted by a phase comparator 10, a low-pass filter 20 and a VCO circuit 40, then comparators 60, 61 for comparing a slice voltage with an output of a peak hold circuit 50 which replaces a VCO control voltage signal outputted from the filter 20 with a DC signal, and a counter circuit 70 for detecting that an EXOR gate 62 taking the exclusive OR of outputs of the comparators 60, 61 is set to HIGH for a specified time, are furnished, then the mode is changed over from a 1st synchronizing mode making the filter 20 have high gain before the specified number of data are read from the start in the read of the magnetic tape, to a 2nd synchronizing mode making the filter 20 have low gain by an output of the counter circuit 70, by a gain switching device 30 when the number of retrying times of the data read of the magnetic tape drive reaches the specified number. <P>COPYRIGHT: (C)2003,JPO |
