Dual error correction code

Abstract

A method of detecting errors in a data stream being transmitted in a computer system, e.g., from a memory array to a memory controller, by determining whether the encoding was performed using a first encoding method or a second encoding method, and thereafter decoding the data stream using a logic circuit based on a single parity-check matrix. The entire parity-check matrix is used to decode the data stream if the first encoding method was used, and a subset of the parity-check matrix is used to decode the data stream if the second encoding method was used. Encoding according to the first method allows correction of all single-symbol errors and detection of all double-symbol errors in the data stream, and encoding according to the second method allows correction of all single-bit errors and detection of all double-bit errors in the data stream. The subset matrix may be permuted if the second encoding method was used, to create a permuted matrix further allowing detection of single-symbol errors. In an exemplary embodiment, the parity-check matrix is a (76,66) matrix and the subset of the parity-check matrix is a (72,64) matrix.