NandFlash Wear-Leveling Bad Block Management
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Solution Overview
Problem
Existing NandFlash memory systems in embedded systems with limited resources face challenges in managing bad blocks and ensuring even wear-leveling, leading to reduced memory lifetime due to insufficient hardware and software resources.
Innovation Solution
A wear-leveling method that creates a file information table to identify and avoid bad blocks, using a swap area to replace faulty blocks and maintain consistent writing operations, with low computational and RAM requirements, dividing the NandFlash memory into storage, file, and swap areas for efficient data management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a common file system driver (e.g., YAFFS) is used to support unlimited files with preparation format, then file reading/writing capability is improved, but hardware and software resource requirements increase
Solution Approach 1:
The patent extracts and removes the complex file system driver layer (YAFFS) from the system. Instead of using a full-featured file system that requires significant RAM and CPU resources, the invention implements a simplified file management mechanism directly in the NandFlash controller that handles only the essential wear-leveling and bad block management functions, thereby reducing hardware and software resource requirements while maintaining core functionality
Solution Approach 2:
The patent replaces expensive, resource-intensive file system software with a lightweight, disposable-style management approach. The simplified file information table and direct mapping mechanism consume minimal RAM (only tens of KB) and CPU cycles, effectively using low-cost, simple structures to achieve the necessary file management capability without the overhead of persistent complex file system drivers
2Quantity of substance
If NandFlash memory is used for data storage with block-based writing, then storage capacity is improved, but the number of writing operations is limited
Solution Approach 1:
The patent implements preliminary action by maintaining a file information table that pre-records the mapping between logical file addresses and physical NandFlash block addresses. Before actual writing operations occur, the system determines the target block and checks its status (good or bad). This advance preparation allows the system to proactively manage wear by selecting optimal blocks for writing and preemptively handling bad blocks, thereby extending the total number of usable writing operations over the memory's lifetime
Solution Approach 2:
The patent changes the operational parameters of NandFlash by implementing wear-leveling algorithms that dynamically adjust writing patterns. The system monitors and equalizes the number of writing operations across different blocks, ensuring uniform wear distribution. Additionally, the system changes the state management of blocks by maintaining detailed status information (good, bad, erased, etc.) and transitioning blocks between states based on wear conditions, thereby maximizing the usable writing operations before the memory reaches end-of-life
3Reliability
If bad blocks are identified and avoided during writing operations, then memory reliability is improved, but additional processing time is required
Solution Approach 1:
The patent applies preliminary action by pre-identifying and marking bad blocks during initial memory characterization or during previous writing operations. The bad block information is stored in the file information table and bad block registration table before actual data writing begins. When a writing operation is initiated, the system immediately checks the pre-prepared mapping information to determine whether the target block is good or bad, eliminating the need for time-consuming runtime detection and allowing proactive selection of alternative blocks if needed
Data Source
AI summary
A wear-leveling NandFlash memory reading/writing method can identify a bad block, avoid the bad block, and equalize writing operations to ensure that all the blocks are identical in number of the writing operations so as to guarantee wear-leveling NandFlash memory reading and writing of the entire memory. This method has characteristics of low computational and small RAM cost, is suitable for the application scenario like operating a single file for a long time with an imbedded system with low cost and poor hardware resource, and can provide a complete file system solution.