DC-free line code and bit and frame synchronization for arbitrary data transmission

摘要

PCT No. PCT/US91/08483 Sec. 371 Date May 5, 1992 Sec. 102(e) Date May 5, 1992 PCT Filed Nov. 13, 1991 PCT Pub. No. WO92/09162 PCT Pub. Date May 29, 1992.A method of encoding data for transmission over a communication link. A cumulative polarity of previously-transmitted frames is maintained. A frame is prepared for transmission by combining a data word with a plurality of additional bits. The additional bits provide a master transition. A phantom bit is encoded in the additional bits. If the polarity of the frame is the same as the cumulative polarity, the data bits or in some instances all the bits are inverted so as to maintain balance. Control words and fill words are provided and are distinguished from data words by encoding the additional bits. Control words carry additional data or control instructions and are distinguished from fill words by the number of transitions. The phantom bit either conveys additional data or is used for such purposes as error checking.