An apparatus for generating codewords in a two-level, block-formatted linear error correction code (ECC), each block comprising a plurality of codewords and a plurality of block-level check bytes derived from the codewords, each codeword comprising data bytes and check bytes derived from the data bytes in the codeword, comprising:
- (a) a first logic arrangement responsive to N extrinsically supplied data byte vectors m for creating a set of N data byte vectors m′ as an interleave of elements of said data vectors m, said first arrangement including circuits for matrix multiplication of the N data byte vectors and a nonsingular invertible integration matrix with nonzero minors up to order B;
- (b) an encoder arrangement for mapping said set of N data byte vectors m′ into a counterpart set of N codewords c′ of a linear ECC code, said set including 2t1 check bytes per codeword and B*(2t2) block-level check bytes;
- and
- (c) a second logic arrangement for creating a set of N modified codewords c from said set of N codewords c′, said second arrangement including circuits for matrix multiplication of the N codewords c′ by the inverse of the integration matrix.