Read Disturbance Management in Non-Volatile Memory Systems
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Solution Overview
Problem
Multilevel-cell (MLC) non-volatile memory systems face reduced reliability due to lower tolerance for read disturbance, which causes data changes in adjacent memory cells after a significantly lower number of reads compared to Single Level Cell (SLC) memory, necessitating effective read disturbance management to prevent data corruption.
Innovation Solution
Implementing a block table in non-volatile memory to record and manage read counts for each memory block, moving data to a new location when the read count reaches a predetermined threshold, thereby preventing read disturbance effects, and resetting the read count data for both the original and new locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If MLC memory is used to increase storage capacity, then storage capacity is improved, but reliability deteriorates due to lower tolerance for read disturbance
Solution Approach 1:
The patent applies preliminary action by proactively moving data to a new location before read disturbance can corrupt adjacent cells. The system monitors read counts and triggers data migration when the threshold is approached, preventing the harmful effect rather than reacting after damage occurs. This is implemented through the block table that tracks read counts and initiates moves before disturbance affects data integrity.
2Reliability
If read count monitoring is implemented to prevent read disturbance, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the block table to serve multiple functions: it stores read count data, tracks memory block locations, manages data migration decisions, and monitors for disturbance conditions. This multi-functional approach consolidates what would otherwise require separate mechanisms into a single structure, reducing overall system complexity while maintaining reliability.
3Reliability
If data is moved frequently to prevent read disturbance, then reliability is improved, but loss of time increases due to migration operations
Solution Approach 1:
The patent applies preliminary action by moving data just before read disturbance occurs, rather than continuously migrating or waiting for damage. This timing optimization minimizes migration frequency to only when necessary, reducing time loss while maintaining data integrity. The threshold-based trigger ensures moves are proactive but not excessive.
Data Source
AI summary
An invention is provided for read disturbance management in a non-volatile memory. The invention includes storing a read count data for a memory location in non-volatile memory. The read count data indicating an amount of read operations accessing the memory location since data was last written to the memory location. Then, when data is read from the memory location while the value of the read count data is less than a predetermined threshold value, the value of the read count data is incremented. However, when the value of the read count data equals the predetermined threshold value, the data is moved to a new memory location, thereby avoiding read disturbance effects.