| 摘要 |
PURPOSE: A data modulator is provided to have smaller DSV(digital sum value) of modulation data by storing the total number of modulation data and DSV as well as modulation data and state information in a modulation table. CONSTITUTION: Primary synchronous codes and conversion data to each code are read and inputted from a modulation ROM(read only memory,736) if the ECC(error correction code)-added data is synchronous. A modulation data selector(400) detects the N included in the modulation data of primary synchronous codes and adds the DSV of primary synchronous codes to the accumulated DSV if the N is 0. Otherwise, the selector calculates DSV1 by subtracting the DSV of primary synchronous codes from the accumulated DSV. The N included in secondary synchronous codes passes through the same process as one in the primary codes. The synchronous modulation data of primary codes is selected if the DSV1 is smaller than DSV2, or the secondary data is selected to output modulation data of synchronous codes of reducing the accumulated DSV data selectively.
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