Importance

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Abstract

A recording medium for a computer contains sectors, each of which represents a section of data that has originally been supplied by a user. As the user data is sent to the recording medium from the memory of the computer, an adjust bit determining circuit determines the adjust bit for a block of the write data. The adjust bit-value is such that the sum of the DC levels for the write data at a given point is equal to zero or approaches zero. The user data is converted using RLL(1,7) codes and PWM is performed to derive the write data. The circuit includes an encoder for receiving the user data two bits at a time. The encoder outputs DSV values for the 2-bit user data. A first circuit group for accumulating the DSV values from the encoder is used acquire block DSV values of data belonging to the plurality of blocks of the data section. A second circuit group accumulates these block DSV values computed by the first circuit group and calculates a temporary sector DSV value. This temporary sector DSV value represents a DSV value ranging from the head block of the data section up to the current block which is being processed. The first and second circuit groups are controlled by a DSV sequencer. A determining circuit is coupled to the first and second circuit groups for comparing the sector DSV value with a block DSV value for a next block following the current block.

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First Claim