Flash Memory Access Frequency Estimation for Wear Leveling
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Solution Overview
Problem
Current methods for verifying wear leveling in flash memory controllers are inadequate, as they either rely on visual verification that cannot detect unpredictable issues or use general-purpose logic analyzers that cannot recognize flash memory-specific commands, making it difficult to ensure even data writing across memory cells and thus compromising data retention reliability.
Innovation Solution
An apparatus and method that estimate access frequency to a flash memory by detecting and analyzing internal signals between the flash memory and its controller, specifically utilizing the characteristic that NAND flash memory erases data in units of blocks, allowing for efficient estimation of writing frequency by monitoring erasure commands and addresses, thereby identifying blocks that need wear leveling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If visual verification of flowchart and simulation are used, then verification process is simple, but actual unpredictable defects in wear leveling cannot be detected
Solution Approach 1:
The patent creates a virtual model (copy) of the flash memory controller's wear leveling operation that mimics actual hardware behavior. This virtual model processes test data and generates access frequency information that reflects real operational characteristics, allowing verification of unpredictable defects without physical hardware while maintaining simplicity.
Solution Approach 2:
The patent introduces a verification tool as an intermediary between the flowchart/simulation stage and actual hardware testing. This tool acts as a mediator that processes control commands and generates wear leveling verification results, bridging the gap between theoretical verification and practical hardware testing.
2Ease of manufacture
If general-purpose logic analyzer is used to monitor bus signals, then hardware is readily available, but flash memory-specific commands cannot be recognized and data processing becomes enormous
Solution Approach 1:
The patent extracts only the essential wear leveling verification functions from the complex bus signal monitoring task. Instead of analyzing all bus signals, it selectively captures and processes only the control commands relevant to wear leveling, significantly reducing data processing complexity while using standard logic analyzer hardware.
Solution Approach 2:
The patent makes the verification tool universal by designing it to handle multiple flash memory command types (read, write, erase commands) through a single integrated processing mechanism. The tool can recognize and process various flash memory-specific commands without requiring different hardware configurations.
3Measurement precision
If all bus signals are monitored and stored for analysis, then complete operation data is obtained, but data volume becomes enormous and throughput is reduced
Solution Approach 1:
The patent applies local quality by focusing measurement resources only on the specific aspects of bus signals that are relevant to wear leveling verification. Instead of uniformly monitoring all signals with equal detail, it selectively captures control commands and their associated parameters, obtaining sufficient verification data with minimal processing overhead.
Solution Approach 2:
The patent performs partial action by capturing only the essential control commands needed for wear leveling verification rather than all possible bus signals. This selective approach provides sufficient information for verification while maintaining high throughput, avoiding the excessive data collection that would reduce productivity.
Data Source
AI summary
An apparatus for estimating a frequency of access to a storage device that includes a flash memory and a controller for controlling the flash memory includes interface. Data is written into the flash memory in units of a page and being erased from the flash memory in units of a block consisting of pages. The interface is supplied with an internal signal transferred between the flash memory and the controller, configured to recognize the internal signal, and outputs the internal signal as an input signal. An erasure sequence detection section outputs a detection signal when address data is followed by an erasure command requesting erasure of data in the block specified by the address data in the input signal. An address holding section holds address data in the internal signal, and outputs held address data as erasure address data when supplied with the detection signal.