Flash Memory Logical Sector Erasure Control
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Solution Overview
Problem
Flash memory experiences data garbling due to erasure disturbance, where frequent erasure causes unintended changes in threshold voltage of non-selected memory cells, leading to loss of storage information.
Innovation Solution
A memory control method that logically divides physical sectors into multiple sectors, performing batch erasure only when no writable logical sectors are present, thereby minimizing erasure stress and preventing data garbling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If frequent erasure is performed in flash memory, then data can be updated regularly, but erasure disturbance causes threshold voltage changes in non-selected cells leading to data garbling
Solution Approach 1:
The memory device is divided into multiple physical sectors, each further divided into multiple logical sectors. This segmentation allows independent erasure of specific logical sectors without affecting others, enabling selective erasure that updates only necessary data regions while preserving other data, thus maintaining data integrity during frequent updates.
Solution Approach 2:
The patent applies different erasure strategies to different logical sectors based on their write status. Fully written logical sectors are erased in batch operations, while sectors with unwritten pages are excluded from erasure. This local differentiation ensures that erasure stress is applied only where necessary, preventing disturbance to non-selected cells while maintaining productivity.
2Productivity
If batch erasure is performed on all logical sectors, then storage space is reclaimed efficiently, but erasure stress is applied to sectors that still contain writable data causing potential data loss
Solution Approach 1:
The erasure operation is made dynamic and adaptive based on the current state of logical sectors. The memory controller checks the write status of each logical sector and dynamically adjusts the erasure scope. Only logical sectors that are fully written are included in batch erasure operations, while sectors with unwritten pages are dynamically excluded, ensuring data safety while maintaining efficient storage reclamation.
Solution Approach 2:
The system uses feedback from the write status of logical sectors to control erasure operations. Before performing batch erasure, the memory controller verifies that target logical sectors have no unwritten pages. This feedback mechanism ensures that erasure is only applied to sectors that are safe to erase, preventing data loss while efficiently reclaiming storage space.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the frequency of erasure stress, ensuring that erasure disturbance is avoided, and data integrity is maintained by applying erasure voltage only when necessary, thus preventing data loss.
Implementation Method 1
erasure disturbance means a change in the amount of charge held in a floating gate of a memory cell in a non-selected state due to a voltage applied to the memory cell in the non-selected state during deletion of a selected cell
Data Source
AI summary
A memory control method includes: writing data in at least one page that is a part of a plurality of logical sectors; erasing the data in at least one of the plurality of logical sectors; and controlling an operation for write and erasure in a memory to which an erasure voltage is applied in a physical sector including the plurality of logical sectors; and performing batch erasure for each of a plurality of logically divided physical sectors obtained by logically dividing the physical sector into at least two sectors.