| 摘要 |
A method for converting a succession of data words into an output bit stream comprising a succession of code words uses a table of code words and associated next state values. For each data word the table provides a code word and associated next state value for each of a plurality of present state values. The code words are either of a first type that correspond to only one data word or of a second type that correspond to more than one data word. The next state value associated with each code word of the second type belongs to one of a first group of states. The next state values ensure that adjacent code words chosen in accordance with the next state values satisfy a run length constraint. Code words belonging to the first group of states can be identified by a unique bit structure. The method comprises the following steps: a) retrieving a data word; b) selecting the code words corresponding to the data word from the others of the plurality of present state values which meet the run length constraint and, if the present state value belongs to the first group of states, which also match the unique bit structure of the present state value; c) selecting, from the code words selected in step b), the encoded word that will cause the dc content of the output bit stream to be closest to zero; and d) placing the encoded word selected in step c) into the output bit stream. |
