Flash Memory Controller Error Threshold Retirement
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Solution Overview
Problem
Conventional flash memory controllers retire cells after a limited number of write-erase cycles, leading to inefficient memory usage as they cease operations once a cell fails, without considering the error correction capabilities.
Innovation Solution
Implementing a flash memory system with an encoder, decoder, and controller that uses error correction codes to continue using flash memory locations until the number of decoding errors reaches a threshold, allowing for extended usage beyond conventional limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flash memory controllers retire cells after a limited number of write-erase cycles, then the reliability of data storage is maintained, but the memory usage efficiency deteriorates and operational lifespan is reduced
Solution Approach 1:
The patent changes the retirement parameter from a fixed cycle count to a dynamic error threshold. The controller continues to use flash memory locations even after write-erase cycle limits are reached, instead retiring them only when the number of decoding errors exceeds a threshold that accounts for error correction code capabilities. This parameter change extends operational lifespan while maintaining reliability through adaptive error monitoring.
2Reliability
If flash memory locations are retired immediately upon failure indication, then data integrity is preserved, but memory capacity utilization deteriorates
Solution Approach 1:
The patent applies partial action by not immediately retiring flash memory locations when failures are detected. Instead, it allows continued operation with monitored error rates, retiring only when errors exceed the correction capability. This partial approach to failure response maintains data integrity while preserving additional memory capacity for use.
Solution Approach 2:
The patent implements feedback through continuous monitoring of decoding errors. The controller reads back data, decodes it using error correction codes, and uses the error count feedback to determine whether to continue using or retire the flash memory location. This feedback mechanism ensures data integrity is maintained while optimizing capacity utilization.
3Duration of action of moving object
If error correction codes are used to extend usage beyond conventional limits, then operational lifespan is improved, but device complexity increases
Solution Approach 1:
The patent uses error correction codes as an intermediary mechanism between the flash memory cells and the controller logic. The ECC system acts as a buffer that allows the controller to tolerate certain levels of cell degradation without immediate retirement. This intermediary approach extends operational lifespan while keeping the added complexity contained within the ECC decoding process rather than requiring fundamental controller redesign.
Data Source
AI summary
An integrated circuit including a first interface, a decoder, and a controller. The first interface is configured to (i) write encoded data in a portion of a flash memory, and (ii) read the encoded data back from the flash memory. The decoder is configured to (i) according to an error correction code, decode the encoded data read back from the flash memory, and (ii) based on the decoded data, determine a number of decoding errors corresponding to the decoded data. The controller is configured to, in response to the number of decoding errors being greater than or equal to a first threshold, cease accessing the portion of the flash memory. The first threshold is less than a number of errors correctable by the error correction code for the portion of the flash memory.