Methods and means for simultaneously correcting several channels in error in a parallel multi channel data system using continuously modifiable syndromes and selective generation of internal channel pointers

In an apparatus for decoding data written into a plurality of channels, means for ascertaining channels in error externally and generating pointer signals thereto, said channel plurality being partitioned into one or more data channels, a first channel containing vertical parity checks of the data channels, and a second channel containing diagonal parity checks taken over all the channels in a predetermined positively or negatively sloped direction, wherein the improvement comprises the combination of:

• means for determining syndromes from the parity checks and data written into the channels;
• means for detecting mismatches between the vertical and diagonal syndromes, intersecting the same error in a known error channel, one syndrome intersecting an unknown error channel;
• and
• means responsive to an external pointer signal designating a known error channel and to a mismatch among the vertical and diagonal syndromes intersecting the same error in the known channel for generating an internal pointer to an unknown error channel as a function of the displacement between the first and subsequent vertical and diagonal syndrome mismatch.

In combination, a parallel multi-channel data handling system, including one or more data channels, and an apparatus for correcting plural channels in error simultaneously, the apparatus comprising:

• means for encoding and writing into a first channel vertical parity checks and for encoding and writing into a second channel diagonal parity checks taken over the channels, including the data channels, in a predetermined, positively or negatively sloped direction;
• means for determining syndromes from the parity checks and data written into the channels;
• means for detecting mismatches between the vertical and diagonal syndromes intersecting the same error;
• means responsive to the detected mismatches for generating pointers designating at least one known channel in error;
• means responsive to pointers designating at least one known channel in error and to the detected mismatches for generating correction signals from at least two syndromes intersecting the same error in the known channel, said mens including means for continuously modifying the value of syndrome diagonally intersecting each error in the known channel as it is detected;
• and
• means for correcting said errors by logically combining the correction signals with original known channel data.