| 摘要 |
A method and apparatus are provided for encoding successive n-bit information words into successive m-bit code words wherein m>n. Each n-bit information word is assigned with a respective set of m-bit code words. Each set of code words is comprised of either two or four words. The words in each two-word set have zero disparity, and their first bits are of opposite logical sets. In the four-word sets, two words have positive disparity and their first bits are of opposite logical sense, and the other two words have negative disparity and their first bits also are of opposite logical sense. The particular m-bit code word that is selected from the set associated with the n-bit word commences with the same bit as the last bit of the immeditely preceding code word, and the selected code word exhibits a disparity that, when combined with the digital sum variation of the preceding encoded code words, reduces the overall digital sum variation toward zero. |
