Storage Device Copy-Back Method Error Inspection
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Solution Overview
Problem
The copy-back operation in nonvolatile semiconductor memory devices often requires error correction, which increases the time needed for the operation and reduces access performance due to the necessity of external copy-back methods when error bits exceed a reference value.
Innovation Solution
A method that performs an inspection read operation using sampling read voltages to determine the number of error bits, allowing for either internal or external copy-back based on the number of error bits detected, with internal copy-back used when error bits are within a reference value and external copy-back used when they exceed it, thereby reducing the need for error correction operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error correction operation is performed during copy-back, then data reliability is improved, but operation time increases and access performance deteriorates
Solution Approach 1:
The patent performs an inspection read operation before the copy-back operation to detect error bits in advance. By identifying data with excessive error bits beforehand, the system can prepare for external copy-back with error correction only when necessary, rather than always performing error correction during copy-back, thus reducing overall operation time while maintaining data reliability.
Solution Approach 2:
The patent dynamically selects between internal copy-back (without error correction) and external copy-back (with error correction) based on the number of error bits detected during inspection read. This dynamic adaptation allows the system to optimize operation time by avoiding unnecessary error correction operations while ensuring data reliability when error bits exceed the reference value.
2Measurement precision
If external copy-back method with error correction is used, then data accuracy is improved, but access performance decreases
Solution Approach 1:
The patent applies error correction only partially - specifically, only when the number of error bits exceeds a reference value. For data with acceptable error levels, internal copy-back is performed without error correction, maintaining high access performance. This partial application of error correction ensures data accuracy for problematic data while preserving productivity for the majority of data that doesn't require correction.
3Productivity
If inspection read operation is performed, then copy-back method selection is optimized, but additional time is consumed
Solution Approach 1:
The inspection read operation is performed as a preliminary step before the actual copy-back operation. Although this adds some inspection time, it enables optimized method selection that reduces the overall copy-back time by avoiding unnecessary external copy-back operations with error correction, thereby improving net productivity.
Data Source
AI summary
A copy-back method of a storage device includes reading a memory data from a source area of the storage device. A number of error bits of the memory data is determined. An inspection read operation is performed if the number of error bits exceeds a reference value. The memory data is written to a destination area of the storage device if the number of error bits does not exceed the reference value.