| 摘要 |
<p>A recording medium for a computer contains sectors, each of which represents a section of data that has originally been supplied by a user. Each of these data sections contains a plurality of blocks (L1....LF) of write data. 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 (34) for receiving the user data two bits at a time. The encoder (34) outputs DSV values for the 2-bit user data. A first circuit group (35, 36, 37, 39) for accumulating the DSV values from the encoder (34) is used to acquire block DSV values of data belonging to the plurality of blocks of the data section. A second circuit group (35, 36, 37, 38., 39) accumulates these block DSV values computed by the first circuit group (35, 36, 37, 39) and calculates a temporary sector DSV value (A). This temporary sector DSV value (A) represents a DSV value ranging from the head block (L1)of the data section up to the current block (LN) which is being processed. The first and second circuit groups are controlled by a DSV sequencer (32). A determining circuit (40) is coupled to the first and second circuit groups for comparing the sector DSV value (A) with a block DSV value (B) for a next block (L(N+1)) following the current block (LN). The determining circuit (40) determines an adjust bit value for the next block (L(N+1)) in such a manner that a new sector DSV value obtained by adding the temporary sector DSV value (A) to the block DSV value (B) of the next block (L(N+1)) approaches zero. <IMAGE></p> |
