Flash Memory Controller Sudden Power-Off Recovery
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Solution Overview
Problem
Sudden power-off events in flash memory devices can damage data, making it difficult to determine the usability of pages belonging to the same word line group, leading to inefficient recovery procedures due to the need to check and move multiple pages.
Innovation Solution
A data processing method where a memory controller scans pages in a current memory block to find the last valid page and word line, and determines the usability of empty pages in the same word line group based on read and erase counts, reducing the number of pages that need to be checked and dummy programmed during the Sudden Power-Off Recovery (SPOR) procedure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the memory controller scans all pages in the current memory block to determine usability of pages in the same word line group, then the reliability of data recovery is improved, but the time required for recovery increases
Solution Approach 1:
The patent extracts the determination of page usability from the entire word line group and applies it selectively. By using read count and erase count information, the controller can identify which pages in the word line group are actually affected by SPO and need recovery, versus which pages remain usable. This selective approach reduces the scanning scope from all pages to only affected pages, thereby reducing recovery time while maintaining reliability.
Solution Approach 2:
The patent performs preliminary actions by maintaining and utilizing read count and erase count metadata before the SPO recovery process. These pre-existing counters enable the controller to quickly determine the impact scope of SPO without performing comprehensive scanning from scratch. The preliminary data about page usage patterns allows for rapid decision-making during recovery operations.
2Reliability
If the memory controller checks and dummy programs all pages in the same word line group after SPO, then the reliability of data integrity is improved, but the number of operations increases
Solution Approach 1:
The patent applies local quality by differentiating the treatment of pages within the same word line group. Instead of uniformly checking and dummy-programming all pages, the controller uses read count and erase count to identify specific local regions (pages) that are actually affected by SPO. Only these affected pages undergo the full recovery process, while unaffected pages are skipped, reducing the total number of operations while maintaining data integrity where needed.
Solution Approach 2:
The patent employs partial action by performing recovery operations only on the necessary subset of pages rather than all pages in the word line group. The read count and erase count information enables the controller to determine the minimal set of pages that require recovery, avoiding excessive operations on pages that remain usable. This partial approach reduces the operational burden while ensuring complete recovery of affected data.
3Productivity
If the memory controller uses read count and erase count to determine page usability, then the productivity of data recovery is improved, but the complexity of determination logic increases
Solution Approach 1:
The patent implements self-service by utilizing the memory device's own built-in read count and erase count metadata to make determination decisions. These counters are naturally maintained during normal operation and require no external intervention or complex external determination logic. The controller simply reads these existing counters to determine page usability, making the system self-sufficient and avoiding the need for additional complex determination mechanisms.
Solution Approach 2:
The patent applies parameter changes by transforming the raw read count and erase count data into meaningful usability determinations. By analyzing the changes in these parameters (comparing current counts to threshold values or patterns), the controller derives actionable information about page usability. This parameter transformation approach converts simple counters into intelligent determination logic, improving productivity without requiring overly complex decision-making structures.
Data Source
AI summary
A data storage device includes a memory controller and a memory device. The memory device includes a current memory block. The memory controller is coupled to the memory device and configured to access the memory device. In response to detection of a sudden power-off that has occurred before the memory device is powered up, the memory controller is configured to find a last valid page and a last valid word line corresponding to the last valid page by scanning a plurality of pages in the current memory block, and determine whether to use one or more empty pages belonging to a word line group that is the same as that of the last valid page according to a read count and an erase count of the current memory block.