Flash Memory Block Management for Uniform Rewrite Distribution
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Solution Overview
Problem
Conventional semiconductor recording apparatuses face issues with non-uniform rewrite distribution across physical blocks, leading to increased writing errors and reduced recording rates, especially during sequential recording of moving images, due to the limited number of rewrites allowed in flash memory.
Innovation Solution
A semiconductor recording apparatus with a block management section and a logical-to-physical conversion table initializing section that manages and updates physical addresses to ensure uniform rewrite distribution across physical blocks, utilizing a logical-to-physical conversion table to handle address management and initialization, thereby preventing concentration of rewrites on specific blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flash memory rewriting is performed without leveling control, then the recording process is simple and fast, but the number of rewrites becomes non-uniform across physical blocks, leading to writing errors when the limit is exceeded
Solution Approach 1:
The patent replaces complex mechanical-level rewrite control (tracking and managing rewrite counts for each physical block) with a simplified logical-level approach. By maintaining a logical-to-physical conversion table that maps logical blocks to physical blocks, the system allows the file system to manage data at the logical level while the conversion table automatically handles physical block allocation, eliminating the need for complex rewrite counting and leveling control mechanisms.
2Productivity
If sequential recording of moving images is performed at high speed, then the recording rate increases, but writing errors occur more frequently due to exceeding rewrite limits on specific blocks
Solution Approach 1:
The patent introduces a logical-to-physical conversion table as an intermediary layer between the file system and the physical flash memory blocks. This conversion table acts as a mediator that automatically manages the mapping between logical blocks (used by the file system for high-speed sequential recording) and physical blocks (stored in the flash memory). By using this intermediary, the system can perform rapid sequential recording without needing to implement complex real-time rewrite counting and block selection logic, thus maintaining both high productivity and reliability.
3Stability of the object's composition
If physical formatting is performed to erase all blocks for uniform rewrite distribution, then rewrite uniformity is achieved, but the operation time becomes excessively long
Solution Approach 1:
The patent extracts the rewrite management function from the physical formatting process. Instead of erasing all physical blocks to achieve uniform rewrite distribution, the system maintains a logical-to-physical conversion table that tracks which logical blocks map to which physical blocks. This allows the system to achieve uniform rewrite distribution by managing logical block allocations through the conversion table, completely avoiding the time-consuming physical formatting operation while still ensuring balanced wear across all physical blocks.
4Loss of time
If logical formatting is performed without updating physical address mappings, then formatting operation is fast, but physical blocks are not uniformly utilized leading to concentrated rewrites on specific blocks
Solution Approach 1:
The patent performs preliminary initialization of the logical-to-physical conversion table during the logical formatting process. By pre-establishing the mapping relationships between logical blocks and physical blocks in the conversion table during formatting (before any data recording occurs), the system ensures that subsequent data recording operations will automatically distribute rewrites uniformly across physical blocks. This preliminary action eliminates the need for time-consuming physical formatting while preventing concentrated rewrites on specific blocks.
Data Source
AI summary
A semiconductor recording apparatus includes a logical-to-physical conversion table 115 showing correspondence between a physical address of said semiconductor memory and a logical address and writes the table to a flash memory 120. On receiving a write command issued from a host device 200, a block management section 114 selects a physical block with reference to said logical-to-physical conversion table, and updates said logical-to-physical conversion table. A logical-to-physical conversion table initializing section 117 updates a physical address corresponding to each logical address of the logical-to-physical conversion table into an invalid address. Accordingly the apparatus can render the number of rewrites of physical blocks uniform irrespective of writing conditions.