| 摘要 |
PROBLEM TO BE SOLVED: To avoid conducting a malreproducing process based on an impossible data pattern by detecting a code interval, which exceeds a maximum code interval of a run length limited code, from the updating situation of an amplitude reference value used in a viterbi decoding process and executing a prescribed process in accordance with the detection output. SOLUTION: At an LMD139, a code interval is detected by counting a portion of enable signals c000en to c111en. In other words, the LMD139 detects the space length of a mark length of not less than 9T in the case of an impossible code interval i.e., in the case of an RLL (1, 7). When a sapce of not less than 9T or a mark is generated in the viterbi decoding process, the information is supplied to a controller as signals LM so that a report is made of the face that an erroneous decoding is executed by an unknown cause. A counter 401 outputs the count value corresponding to a space period length. Moreover, a counter 402 outputs the count value corresponding to a mark period length.
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