Flash Memory Controller Read-Disturbance Block Selection
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Solution Overview
Problem
Flash memory cells experience threshold voltage distribution changes due to retention and read disturbances, leading to erroneous data reads, especially under high temperatures, which existing technologies fail to adequately address.
Innovation Solution
A flash memory controller method that determines blocks prone to read disturbances by tracking read counts and time stamps, using a read count and threshold time mapping table to identify blocks for garbage collection, ensuring only those with significant shifts are targeted for data relocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If flash memory is used for data storage, then high storage density and low cost per bit are achieved, but threshold voltage distribution changes due to retention and read disturbances cause erroneous data reads
Solution Approach 1:
The system proactively identifies blocks prone to read disturbances by tracking read counts and time stamps before actual read errors occur. By calculating time differences and comparing against a mapping table, the system relocates data from at-risk blocks to safe blocks in advance, preventing erroneous reads rather than detecting them after they happen.
Solution Approach 2:
The system continuously monitors block usage patterns through read counts and time stamps, using this feedback to dynamically identify blocks requiring garbage collection. The mapping table stores historical data that provides feedback on the relationship between read frequency, retention time, and threshold voltage shifts, enabling adaptive block management.
2Reliability
If all blocks are subjected to garbage collection operation, then data integrity is improved, but system efficiency and productivity deteriorate due to unnecessary data relocation
Solution Approach 1:
Instead of applying garbage collection uniformly to all blocks, the system identifies specific blocks with local quality issues by analyzing individual block characteristics (read count, time stamp, calculated age). The mapping table provides threshold values that vary based on read frequency and retention time, enabling selective garbage collection only for blocks that exceed the disturbance thresholds.
Solution Approach 2:
The system uses parameter changes in the mapping table that correlate read count and threshold time to determine garbage collection necessity. By adjusting the criteria based on these parameters, the system dynamically determines which blocks require intervention, optimizing the balance between data integrity and system efficiency.
3Measurement precision
If read count and time stamp tracking is implemented, then blocks prone to read disturbance are accurately identified, but device complexity increases
Solution Approach 1:
The flash memory blocks essentially tag themselves for garbage collection by having their read counts and time stamps automatically tracked by the controller. The mapping table serves as a reference that requires minimal processing, and the system self-identifies problematic blocks through simple comparisons rather than requiring complex analysis algorithms.
Data Source
AI summary
The present invention provides a control method of a flash memory controller, wherein the flash memory controller is configured to access a flash memory module, and the flash memory module includes a plurality of blocks. The control method includes the steps of: obtaining a read count of a specific block; obtaining a time stamp of the specific block, wherein the time stamp is a write time of the specific block; calculating a time difference between a current system time and the time stamp of the specific block; and using the read count of the specific block and the time difference, and referring to a read count and threshold time mapping table to determine whether to arrange the specific block in a garbage collection pool.