| 摘要 |
PURPOSE:To eliminate the need for detecting a special pattern for reading positioning information and to attain the positioning action with high reliability by providing a first frequency-dividing device and a second frequency-dividing device, and setting the rise or fall part of respective rectangular waves of a second frequency-dividing device output signal so as to be used as the special conditions. CONSTITUTION:A basic clock signal 11 is frequency-divided by the first frequency- dividing device 2 and the number of rotation of a spindle motor 6 is controlled so as to come to be the same phase as a first frequency-dividing device output signal 12. On the other hand, a second frequency-dividing device output signal 17 of the output of the second frequency-dividing device is also synchornized to the rotation of the spindle motor 6. Here, the number of frequency-divisions of the second frequency-dividing device is set so that the part of rise or fall of respective rectangular waves of the output signal can be coincident wit the starting position of the positioning information or the frequency of the basic lock signal 11 can be the least common denominator of the frequency of the first frequency-dividing device output 12 and the frequency of the second frequency-dividing device output signal 17. Thus, the position in which the positioning information of the magnetic head exists, can be recognized without detecting a special pattern.
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