Two bit symbol SEC/DED code

Claim 1

In an error correction system having a single bit error correction code and double error detection code for a memory in which bits of memory data words are divided into N packages of M bits per package, modularized error correction apparatus for correcting package errors including: encoder means for encoding data words into code words in accordance with an N bit single error correction double error detection code that was expanded to cover N packages of M bits each so that the Exclusive-OR of all M single bit error syndromes in any given package N results in a composite syndrome which is unique for each package, decoder means including means comparing each single bit error syndrome with all possible single bit error syndromes and all possible composite syndromes to determine the location of any single bit error, any single package failure and to detect all double bit errors and all double package failures; and correction means for correcting errors located by said decoder means.