Flash Memory Cell Wear-Leveling via Binary Data Counting
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Solution Overview
Problem
Existing wear-leveling algorithms for flash memory devices operate at the block level, leading to uneven wear across flash blocks due to varying numbers of '0's and '1's being written, causing some blocks to wear out significantly faster than others, despite equal erase-write cycles.
Innovation Solution
A cell-based wear-leveling method that counts the number of '0's and '1's in incoming data chunks and distributes writing across cells to maintain even wear, using wear-leveling information to identify the least and most worn-out cells for optimal data placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If block-level wear-leveling is used to distribute erase-write operations evenly across flash blocks, then the number of erase cycles per block is balanced, but the actual wear on cells remains uneven due to varying numbers of '0's written to different blocks
Solution Approach 1:
The invention segments the wear-leveling granularity from block level to cell level. Instead of treating entire flash blocks as the unit for wear distribution, the system tracks and distributes wear at the individual cell level within blocks. This is achieved by maintaining wear counters for each cell and selectively erasing only the necessary cells rather than entire blocks, thereby achieving more precise wear control.
Solution Approach 2:
The invention applies local quality by treating different cells within the same block differently based on their individual wear states. The system identifies specific cells that have accumulated excessive wear (high '0' count) and targets them for erasure, rather than uniformly erasing entire blocks. This localized approach ensures that wear is distributed more evenly across all cells regardless of their block assignments.
2Productivity
If flash blocks are erased and rewritten with equal frequency, then block-level wear appears balanced, but cells within blocks experience different wear due to random data patterns with varying numbers of '0's
Solution Approach 1:
The invention performs preliminary action by proactively tracking the wear state of each cell through wear counters that monitor the number of '0's written to each cell. Before a cell reaches its endurance limit, the system identifies it as needing erasure and schedules it accordingly. This preventive approach allows the system to redistribute wear before critical failure occurs, rather than reacting after damage has accumulated.
Solution Approach 2:
The system implements feedback mechanisms by continuously monitoring wear counters for each cell and using this information to make dynamic decisions about which cells to erase and rewrite. The wear counter data feeds back into the wear-leveling algorithm, which adjusts erasure and write operations in real-time to maintain even wear distribution across all cells, thereby extending overall device lifespan.
Data Source
AI summary
A method for wear-leveling cells, pages, sub-pages or blocks of a memory such as a flash memory includes receiving (S10) a chunk of data to be written on the cell, page, sub-page or block of the memory; counting (S40), in the received chunk of data, a number of times a given type of binary data ‘0’ or ‘1’ is to be written; and distributing (S50) the writing of the received chunk of data among cells, pages, sub-pages or blocks of the memory such as to wear-level the memory with respect to the number of the given type of binary data ‘0’ or ‘1’ counted in the chunk of data to be written.