Default Read Signal Selection for NAND Flash Memory
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current memory systems face challenges in setting an optimal read signal for data retrieval from memory cells, leading to errors due to the use of single read signals that may not accurately represent the stored data states, especially in non-volatile memory arrays like NAND flash memory.
Innovation Solution
The method involves reading data from memory cells using multiple discrete read signals, error correcting the data, and setting a default read signal based on the results to minimize errors, which can vary by location within the memory array or by page type, thereby optimizing data retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single read signal is used for data retrieval from memory cells, then the read operation is simple and fast, but errors occur because the read signal may not accurately represent the stored data states
Solution Approach 1:
The read signal is segmented into multiple discrete read signals (first read signal, second read signal, etc.) with different magnitudes. Each read signal targets specific data states, allowing accurate retrieval of multi-level data from memory cells without requiring a single complex signal
Solution Approach 2:
Instead of using a single read signal that attempts to read all data states, the method applies multiple read signals where each signal is optimized for specific data states. This partial action approach reads data in stages, correcting errors progressively rather than requiring one perfect read signal
2Measurement precision
If multiple discrete read signals are used to improve data accuracy, then error correction improves, but the read operation complexity increases
Solution Approach 1:
The method incorporates error correction feedback between read operations. After reading with the first read signal, error correction is applied, then the second read signal is used with another error correction pass. This feedback mechanism improves measurement precision while managing complexity through iterative refinement rather than requiring all signals to be perfectly optimized simultaneously
Solution Approach 2:
Error correction is performed preliminarily after each read signal before proceeding to the next read signal. This preliminary action reduces the burden on subsequent read signals, allowing them to focus on specific data states rather than needing to compensate for all possible errors, thereby managing overall operation complexity
3Measurement precision
If test data writes are performed to determine optimal read signals, then read accuracy improves, but memory device wear increases
Solution Approach 1:
The system uses self-service by performing error correction on actual data reads rather than requiring external test data writes. The error correction unit analyzes read errors from normal operational data and uses this information to optimize subsequent reads, eliminating the need for separate test procedures that would cause additional wear
Solution Approach 2:
Instead of writing physical test data to memory cells to characterize read behavior, the method creates a logical copy of read error patterns through error correction analysis. This virtual modeling of read characteristics allows optimization without physical test writes, preventing wear while achieving the same goal of read signal optimization
Data Source
AI summary
The present disclosure includes apparatuses and methods related to setting a default read signal based on error correction. A number of methods can include reading a page of data from a group of memory cells with a first discrete read signal and error correcting at least one codeword of the page of data as read with the first discrete read signal. Methods can include reading a page of data from the group of memory cells with a second discrete read signal different than the first discrete read signal and error correcting at least one codeword of the page of data as read with the second discrete read signal. One of the first and the second discrete read signals can be set as a default read signal based at least in part on the respective error corrections.