Nonvolatile Memory Refresh via Power Cycle Scanning
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Solution Overview
Problem
Flash memory devices experience data corruption and read errors due to external factors like cosmic rays and frequent program-induced disturbances, leading to unreliable data storage over time, especially in devices that undergo frequent power cycles.
Innovation Solution
Implementing a power cycle-based and background memory refresh method that systematically scans and refreshes nonvolatile memory blocks to prevent data corruption by copying and reprogramming data when error thresholds are exceeded, using error correction codes to correct errors and minimizing the number of programming operations during device startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If frequent power cycles occur, then device adaptability improves, but memory reliability deteriorates due to data corruption from cosmic rays and program-induced disturbances
Solution Approach 1:
The patent implements a refresh operation that proactively copies data from nonvolatile memory to volatile memory and back before corruption occurs. This preliminary action prevents data loss by restoring data integrity periodically, addressing the reliability issue caused by frequent power cycles and cosmic ray exposure.
Solution Approach 2:
The system monitors memory block status and determines when refresh operations are needed based on read error thresholds. When the number of read errors exceeds a threshold, the system triggers a refresh operation, creating a feedback loop that maintains memory reliability adaptively based on actual error conditions.
2Reliability
If systematic memory scanning and refresh operations are performed, then memory reliability improves, but system productivity deteriorates due to refresh operations impacting availability
Solution Approach 1:
The patent implements periodic refresh operations triggered by power cycle counters rather than continuous scanning. The memory controller performs refresh operations at intervals determined by power cycle frequency, reducing the overall burden on system availability while maintaining reliability through periodic data restoration.
Solution Approach 2:
The system performs refresh operations selectively on memory blocks that require it, rather than scanning and refreshing the entire memory space continuously. By targeting only affected blocks and using error threshold monitoring, the system achieves adequate reliability with reduced productivity impact.
3Ease of operation
If the number of programming operations is minimized during startup, then device ease of operation improves, but memory reliability deteriorates due to insufficient refresh coverage
Solution Approach 1:
The patent performs refresh operations during the power-on sequence before the system becomes fully operational. By completing data copying and reprogramming during startup, the system ensures memory reliability is established before normal operation begins, without requiring additional programming operations during active use.
Data Source
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AI summary
Apparatuses and memory refresh methods are disclosed, such as those involving checking a portion of a memory device for errors in response to the memory device being powered on, and reprogramming corrected data to the memory device if errors are found in checking the portion of the nonvolatile memory for errors. Other apparatuses and memory refresh methods are disclosed.