Memory Controller Read Error Testing for Bad Block Detection
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Solution Overview
Problem
Flash memory devices experience read errors due to threshold voltage shifts caused by usage, environmental changes, and manufacturing defects, leading to data loss and increased read delays as existing error handling mechanisms fail to identify and manage bad blocks effectively.
Innovation Solution
A memory test is performed on blocks with read errors to determine if they malfunction, allowing identification of irrecoverable defects and labeling them as bad blocks, preventing further data loss and reducing read delays by avoiding repeat erasing and writing operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error handling mechanisms are repeatedly applied to blocks with read errors, then attempts to recover data are made, but read delays increase and data loss occurs when blocks are actually defective
Solution Approach 1:
The patent performs a memory test on blocks exhibiting read errors to preliminarily determine whether they are defective before attempting data recovery. This preliminary classification prevents time-consuming error handling operations on actually defective blocks, thereby reducing read delays while maintaining data integrity through targeted recovery attempts only on recoverable blocks.
2Reliability
If error handling mechanisms are applied to all blocks with read errors, then potential data recovery is attempted, but system complexity increases due to frequent error handling operations
Solution Approach 1:
The patent applies different handling strategies to different blocks based on their test results: blocks identified as defective are immediately marked and excluded from error handling, while blocks with temporary errors undergo standard error handling procedures. This localized differentiation reduces overall system complexity by avoiding unnecessary error handling operations on defective blocks while maintaining recovery capability for recoverable blocks.
3Loss of time
If blocks with read errors are immediately marked as bad blocks, then read delays are reduced by avoiding further operations, but false positives occur when blocks could actually be recovered
Solution Approach 1:
The patent performs a memory test as a preliminary action before marking blocks as bad, allowing differentiation between permanently defective blocks and those with temporary errors. Blocks that fail the memory test are confidently marked as bad to prevent future read delays, while blocks passing the test continue to undergo error handling, thus avoiding false positives and potential data loss while maintaining fast read performance.
Data Source
AI summary
A method for handling a read error on a block of a memory device is disclosed. In response to a read failure indicating that at least one error handling mechanism has handled the read error on the block and fails to read data stored in the block, a memory test is trigged to be performed on the block. The memory test is configured to determine whether the block malfunctions.