Nonvolatile Memory Write Completion Flag Table
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Solution Overview
Problem
Multiple-valued NAND flash memory devices cannot perform partial writing to a page, making it impossible to write a writing completion flag in the management region, which compromises writing rate and reliability, especially in large-capacity storage systems like 512-MB main storage memory, leading to a significant reduction in usable data recording capacity.
Innovation Solution
A semiconductor memory device with a non-volatile main storage memory and a control memory that stores a writing completion flag table, allowing the flag to be written in a separate control memory, enabling higher writing rates and maintaining reliability by using a higher writing-rate memory like FeRAM for the control memory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple-valued NAND flash memory is used as main storage memory, then large capacity at low cost is achieved, but partial writing to a page becomes impossible, making it unable to write writing completion flag in management region
Solution Approach 1:
The patent divides the storage system into two separate parts: the main storage memory (multiple-valued NAND flash) for data storage, and a control memory (binary flash or FeRAM) for storing writing completion flags. This segmentation allows each component to perform its optimal function - the main storage provides large capacity while the control memory enables fast flag writing and reliable status tracking.
Solution Approach 2:
The control memory acts as an intermediary between the host system and the main storage memory. It stores the writing completion flag table that tracks the status of writing operations to the main storage, enabling the system to determine whether data was successfully written even when power is lost, without requiring the main storage memory itself to support partial page writing.
2Reliability
If writing completion flag is written in management region of main storage memory, then reliability is improved, but writing rate decreases due to inability to perform partial writing
Solution Approach 1:
The patent separates the flag storage function from the data storage function by using a dedicated control memory. This allows writing completion flags to be updated quickly in the control memory without requiring slow partial page writes to the main storage memory, thus maintaining both high reliability and high writing rate.
Solution Approach 2:
The patent changes the physical state or type of memory used for storing writing completion flags from the main storage memory (multiple-valued NAND flash with slow partial write) to a control memory (binary flash or FeRAM) that supports fast writing operations, thereby improving the writing rate while maintaining reliability.
3Reliability
If separate physical region is allocated for writing completion flag in 512-MB main storage memory, then reliability is secured, but usable region for data recording is significantly reduced
Solution Approach 1:
The patent segments the storage system into main storage memory for data and a separate control memory for management information. The control memory has minimal capacity (sufficient only for flag tables) and does not reduce the usable capacity of the main storage memory, as it is a distinct component rather than a region within the main storage.
Solution Approach 2:
The patent moves the writing completion flag storage from the same dimensional space as data storage (within the 512-MB main storage memory) to a different dimensional space (a separate control memory component). This eliminates the trade-off between flag storage and data capacity by placing them in separate memory hierarchies.
Data Source
AI summary
A writing completion flag table that stores a writing completion flag corresponding to a predetermined storage, such as a cluster or a physical block, is stored in a non-volatile control memory. When completion of data writing into a predetermined storage is detected, a write completion flag is written in the corresponding address of the storage on the write completion flag table. Thus, it is possible to recognize that data has been written normally. Even when the flag indicating completion of writing into a page of the writing unit of the main storage memory cannot be written, it is possible to improve the writing reliability.