Flash Memory Block State Management via Non-Volatile Flag Backup
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Solution Overview
Problem
Flash memory and other semiconductor memories face issues with data reliability due to defective blocks, which can be misidentified as valid blocks after block state management is lost or erased, leading to reduced data reliability and potential data loss.
Innovation Solution
A control device with a storage system that includes a first storage area for data that can be rewritten and a second storage area for flag management information, where flags indicate block usability, allowing for reliable data storage by managing defective blocks through flag management and backup processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If block state management means are stored in the flash memory and generated on memory means including volatile memory at system initialization, then data reliability is improved by tracking defective blocks, but the system becomes vulnerable to data loss when the block state management means are erased or lost, as defective block identification information disappears from the flash memory
Solution Approach 1:
The patent creates a copy of the block state management means and stores it in a non-volatile memory region within the flash memory. This copy preserves defective block identification information even when the volatile memory is erased or lost, preventing data loss while maintaining reliability tracking capabilities.
Solution Approach 2:
The patent performs preliminary action by pre-storing the block state management means in a non-volatile memory region before the volatile memory is erased or lost. This ensures that defective block identification information is preserved in advance, preventing information loss during subsequent operations.
2Ease of manufacture
If all blocks of the flash memory are erased to re-create block state management means, then the system can regenerate defective block tracking, but the process causes defective block identification information to disappear and misidentify valid blocks as defective
Solution Approach 1:
The patent uses a copy of the block state management means stored in non-volatile memory as a reference during regeneration. This copy preserves the original defective block identification information, allowing the system to regenerate tracking accurately without misidentifying valid blocks as defective.
Solution Approach 2:
The patent implements feedback by using the stored copy of block state management means to guide the regeneration process. The copy provides reference information about which blocks are actually defective, enabling accurate regeneration without the errors that would occur without this feedback reference.
3Device complexity
If the flash memory is used for both data storage and block state management, then device complexity is reduced, but the risk of data loss increases when block state management information is erased or lost
Solution Approach 1:
The patent segments the flash memory into distinct regions: a first storage area for user data and a second storage area for block state management means. This segmentation isolates the management information from user data, preventing accidental erasure or loss of management information while maintaining a relatively simple overall structure.
Solution Approach 2:
The patent creates a copy of the block state management means and stores it in the second storage area of the flash memory. This copy serves as a backup that prevents data loss in case the primary management information is erased or lost, enhancing reliability without significantly increasing complexity.
Data Source
AI summary
A control device including: a storage device that includes a first storage area including a plurality of blocks into which data can be written more than once and a second storage area into which data can be written only once, wherein the first storage area further stores a flag for each of the blocks, the flag indicating whether or not the block is allowed to be used; a flag management information creation unit configured to create, on the basis of the flag, a flag management information for managing whether or not data can be stored in each block of the storage device; and a management information controller configured to cause the flag management information to be stored in the second storage area.