Bit-interleaved rate 16/17 modulation code with three-way byte-interleaved ECC

A modulation code encoder for generating a rate 16/17 modulation code for transferring user digital data bytes having a three-way ECC interleave through a data transfer channel comprising:

• a shuffler for shuffling incoming user bytes U.sub.0 U.sub.1 U.sub.2 U.sub.3 U.sub.4 U.sub.5 U.sub.6 U.sub.7, . . . to:
• U.sub.0 U.sub.1 U.sub.3 U.sub.2 U.sub.4 U.sub.5 U.sub.7 U.sub.6, . . . , and for putting out A.sub.i B.sub.i byte pairs of shuffled bytes,
• a byte encoder for encoding eight bits of the Ai bytes of the AiBi byte pairs in accordance with a predetermined rate 8/9 modulation code wherein the encoder selectively encodes shuffled bytes into codewords:
• A.sub.0 B.sub.0 .vertline.A.sub.1 B.sub.1 .vertline..vertline..vertline.A.sub.2 B.sub.2 .vertline.A.sub.3 B.sub.3 .vertline..vertline..vertline.. . . , wherein Ai represents nine-bit rate 8/9 RLL (d=0,k=3) encoded symbols to produce nine code bits a0-a8, and wherein Bi represents unencoded bytes, and
• an interleave circuit for interleaving the nine code bits a0-a8 of each Ai byte with eight bits of each unencoded Bi byte in accordance with a sequence:
• ababababababababa.vertline.ababababababababa.vertline.ababababababababa.ver tline.a . . . ,
• where "a" represents a bit position within an encoded nine-bit symbol Ai, and where "b" represents a bit position within an unencoded byte Bi, to generate the rate 16/17 modulation code.