Memory Controller Read Modes for Partial Soft-Decision Output
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The read latency required to output soft decision data in memory systems degrades the read performance of memory systems, such as solid state drives (SSDs) and memory cards, due to the increased time needed for error correction using soft decision data, which affects the overall efficiency of data retrieval.
Innovation Solution
A memory controller and device configuration that selectively sets read modes based on reliability information, allowing for partial or all-soft decision data read modes to minimize read latency and improve performance by optimizing the output of hard and soft decision data based on cell region degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soft decision data is output for error correction, then data reliability is improved, but read latency increases
Solution Approach 1:
The memory device is divided into multiple cell regions, with different read modes applied to each region. Some regions output only hard decision data for fast reading, while other regions output soft decision data for improved reliability. This segmentation allows the system to balance between read latency and data reliability by selectively applying soft decision processing only where needed.
Solution Approach 2:
Different quality levels of data output are applied to different cell regions based on their degradation characteristics. Regions with lower degradation use fast hard decision read mode, while regions with higher degradation use soft decision read mode for better reliability. This local quality approach optimizes the overall system performance by matching the data processing method to the actual condition of each memory region.
2Reliability
If soft decision data read mode is used for all cell regions, then error correction capability is improved, but read performance deteriorates
Solution Approach 1:
The memory device is divided into multiple cell regions, with different read modes applied to each region. Some regions output only hard decision data for fast reading, while other regions output soft decision data for improved reliability. This segmentation allows the system to balance between read latency and data reliability by selectively applying soft decision processing only where needed.
Solution Approach 2:
Instead of applying soft decision read mode to all cell regions, the patent applies it only to specific regions where degradation is detected. This partial action approach maintains high read performance for undegraded regions while providing enhanced error correction only where necessary, avoiding the performance penalty of universal soft decision processing.
3Loss of time
If hard decision data is selectively read from first cell region, then read latency is reduced, but data reliability may deteriorate in degraded regions
Solution Approach 1:
The memory controller monitors reliability information from the memory device and dynamically adjusts the read mode for different cell regions. When degradation is detected in specific regions, the controller switches those regions to soft decision read mode while maintaining hard decision mode in healthy regions. This feedback mechanism ensures that read latency is minimized in healthy regions while reliability is maintained in degraded regions.
Solution Approach 2:
The read mode for each cell region is not fixed but dynamically adjusted based on the degradation status. The system can switch between hard decision mode and soft decision mode for different regions depending on their condition, allowing optimal performance and reliability at different times as memory degradation progresses unevenly across regions.
Data Source
AI summary
An operating method of a memory controller configured to control a memory device, the operating method includes setting a read mode of the memory device to one of a normal read mode, a partial soft decision (SD) data read mode, and an all-SD data read mode, based on first reliability information and second reliability information representing a degree of degradation of the memory device, selectively receiving hard decision (HD) data, which is read from a first cell region of the memory device, in response to outputting a first read command for the first cell region of the memory device in the partial SD data read mode, and receiving HD data and SD data, which are read from a second cell region of the memory device, in response to outputting a second read command for the second cell region of the memory device in the partial SD data read mode.