Sub-Block ECC Recovery for Uncorrectable Memory Data Errors

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Solution Overview

Problem

Existing error correction coding (ECC) schemes in memory devices are insufficient to correct errors caused by manufacturing processes such as polishing and reflow, which can lead to data corruption beyond the ECC's correction capability.

Innovation Solution

Providing additional ECC data external to the data blocks, specifically corresponding to sub-blocks, to enable correction of errors exceeding the main ECC's capability, by using additional parity dedicated to individual sub-blocks, thereby enhancing error correction capabilities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If additional ECC data is provided for each sub-block, then error correction capability is improved, but memory storage density is reduced

Engineering Contradiction:

Improveerror correction capabilityVSAvoidmemory storage density

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The data block is divided into multiple sub-blocks, and separate ECC data is provided for each sub-block. This segmentation allows targeted error correction for specific sub-blocks that experienced errors during manufacturing processes, improving overall reliability without requiring ECC for the entire data block.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Additional ECC data is applied locally to specific sub-blocks that require error correction rather than uniformly to the entire data block. This local quality approach provides enhanced protection where needed while maintaining standard protection elsewhere, optimizing the balance between reliability and storage density.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If main ECC data is used for the entire data block, then manufacturing cost is reduced, but error correction capability for severe errors is insufficient

Engineering Contradiction:

Improvemanufacturing costVSAvoiderror correction capability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

Instead of applying full ECC protection uniformly to the entire data block (excessive action), the patent applies additional ECC data only to specific sub-blocks that require it (partial action). This approach maintains cost-effectiveness while providing sufficient error correction capability for severe errors in critical areas.

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If additional ECC data is stored in memory, then data integrity is improved, but available memory space is reduced

Engineering Contradiction:

Improvedata integrityVSAvoidavailable memory space

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

Additional ECC data is stored separately for specific sub-blocks rather than for the entire data block. This segmentation of ECC storage provides targeted data integrity protection while minimizing the total amount of memory space consumed by ECC data.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS8484542B2Data recovery using additional error correction coding data

Publication Date: 2013.07.09 SANDISK TECHNOLOGIES LLC

AI summary

A method in a data storage device receiving data including a data block and main error correction coding (ECC) data for the data block. The data block includes a first sub-block of data and a second sub-block of data. The method also includes initiating an ECC operation to process the data block using the main ECC data. In response to the ECC operation indicating uncorrectable errors in the data block, first additional ECC data that is external to the data block is retrieved and a second ECC operation is initiated to process the first sub-block of data using the first additional ECC data.