Nonvolatile Memory Data Recovery via Distribution Table
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Solution Overview
Problem
Nonvolatile memory devices face challenges in maintaining data reliability due to slow write and read speeds, and existing error correction methods are inefficient in handling errors caused by variations in threshold voltage levels of memory cells.
Innovation Solution
A data recovery method that utilizes a distribution table to store recovery read level intervals based on threshold voltage levels, allowing for error correction by comparing measurement data with normal data using a measurement read level, and selecting an appropriate recovery read level interval to correct errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nonvolatile memory device is used to retain data without constant power supply, then data reliability is improved, but write and read speeds become relatively slow
Solution Approach 1:
The system performs preliminary actions by measuring threshold voltage levels of memory cells during normal operation and storing this information in a distribution table. This pre-measurement and pre-storage enables the system to quickly determine optimal read levels for error correction without requiring additional measurement time during actual data retrieval operations.
Solution Approach 2:
The system implements feedback by continuously monitoring read errors and using this information to adjust future read operations. When errors are detected, the system refers to the distribution table of threshold voltage measurements to determine appropriate read level adjustments, creating a closed-loop feedback mechanism that improves reliability while maintaining performance.
2Reliability
If error correction is performed by re-reading data at different read levels, then data reliability is improved, but operation time increases
Solution Approach 1:
The system performs preliminary measurement and classification of threshold voltage distributions during normal operation, storing the results in a distribution table. This pre-computed information eliminates the need for time-consuming real-time analysis of voltage distributions during error correction operations.
Solution Approach 2:
The system creates a copy of the distribution table that maps different read level intervals to their corresponding threshold voltage characteristics. This lookup table approach allows the system to quickly determine the appropriate read levels for error correction without performing complex calculations or measurements during the correction process.
3Reliability
If multiple read levels are used for error correction, then data reliability is improved, but device complexity increases
Solution Approach 1:
The system segments the read level management into distinct components: a distribution table for storing threshold voltage characteristics, a lookup mechanism for retrieving appropriate read levels, and an error detection unit for triggering correction. This segmentation simplifies the overall complexity by dividing the error correction function into manageable, independent modules.
Solution Approach 2:
The distribution table acts as an intermediary between the error detection unit and the read operation unit. Instead of directly managing multiple read levels and threshold voltage calculations, the intermediary table stores pre-computed relationships, allowing the system to simplify the decision-making process during error correction operations.
Data Source
AI summary
A nonvolatile memory system includes a nonvolatile memory device including a distribution table suitable for storing recovery read level intervals that are set by being changed through multiple stages according to a distribution value of threshold voltage levels of a plurality of memory cells, measured at a reference read level, is changed through the multiple stages; and a memory controller suitable for reading measurement data from the memory cells by additionally using a measurement read level, searching for a difference value between the normal data and the measurement data from the multiple stages of distribution values stored in the distribution table, and recovering the normal data based on a recovery read level interval corresponding to a searched distribution value, when an error occurs in normal data read from the memory cells by using the reference read level.