Analog Memory Cell Re-Read Using Suspect ECC Values
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Solution Overview
Problem
Existing data retrieval methods from analog memory cells involve multiple read operations, which increase the number of operations and information volume, limiting data retrieval speed, especially when ECC decoding is performed in a separate device and results are transferred over a limited-bandwidth interface.
Innovation Solution
The method involves initially reading storage values from analog memory cells using a certain threshold, identifying suspect values that may cause ECC decoding failure, re-reading these values using different thresholds, and transferring only the re-read results to the ECC decoder for re-decoding, thereby reducing the volume of information transferred and focusing on suspect values that affect decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple read operations are performed to ensure accurate data retrieval from analog memory cells, then data accuracy is improved, but data retrieval speed deteriorates due to increased number of operations and information volume
Solution Approach 1:
The patent extracts and identifies only the suspect storage values that may have caused ECC decoding failure, rather than re-reading all storage values. This selective extraction approach maintains data accuracy by focusing on problematic values while significantly reducing the volume of data that needs to be re-read and transferred, thus resolving the contradiction between reliability and speed
Solution Approach 2:
The patent segments the re-read operation into two distinct phases: first reading all storage values and attempting ECC decoding, then selectively re-reading only the suspect values that caused decoding failure. This segmentation allows the system to maintain high data accuracy through comprehensive initial reading while achieving faster retrieval speeds through targeted re-reading of only necessary portions
2Reliability
If all read results are transferred to the ECC decoder for decoding, then decoding accuracy is improved, but the volume of information transferred increases, limiting retrieval speed when using limited-bandwidth interfaces
Solution Approach 1:
The patent applies the extraction principle by identifying and isolating only the suspect storage values that are likely to have caused ECC decoding failure. Instead of transferring all read results to the ECC decoder, the system extracts and transfers only the problematic values, thereby maintaining decoding accuracy while dramatically reducing the quantity of data transferred over limited-bandwidth interfaces
3Reliability
If re-read operations are performed on all memory cells, then data retrieval reliability is improved, but the time and operations required increase significantly
Solution Approach 1:
The patent uses the extraction principle to identify and isolate only the suspect storage values that may have caused ECC decoding failure. By extracting and re-reading only these specific problematic values rather than all storage values, the system maintains high data retrieval reliability while significantly reducing the time and operational overhead associated with re-reading operations
Solution Approach 2:
The patent applies partial action by performing re-read operations on only a subset of storage values (those identified as suspect) rather than all storage values. This partial re-reading approach provides sufficient reliability improvement to resolve ECC decoding failures while avoiding the excessive time cost of re-reading the entire set of storage values
Data Source
AI summary
A method for data storage includes storing data, which is encoded with an Error Correction Code (ECC), in a group of analog memory cells by writing respective first storage values to the memory cells in the group. After storing the data, respective second storage values are read from the memory cells in the group, and the read second storage values are processed so as to decode the ECC. Responsively to a failure in decoding the ECC, one or more of the second storage values that potentially caused the failure are identified as suspect storage values. Respective third storage values are re-read from a subset of the memory cells that includes the memory cells holding the suspect storage values. The ECC is re-decoded using the third storage values so as to reconstruct the stored data.