Nonvolatile Memory APL Completion Detection After Power Loss
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Solution Overview
Problem
Memory systems face issues with incomplete active performance loss (APL) task completion detection, leading to potential malfunction and unintended consequences due to the use of outdated APL management data after a power loss event.
Innovation Solution
The technology involves writing a first value to a first location and a second value to a second location in nonvolatile memory before a power loss event, comparing these values upon power restoration to ensure the use of the most recent APL management data, thereby preventing the use of incomplete APL task data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single location in nonvolatile memory is used to store APL management data, then the device complexity is reduced, but the reliability deteriorates due to inability to detect incomplete task completion
Solution Approach 1:
The patent divides the APL management data storage into two separate locations: a first location for storing initial APL management data and a second location for storing updated APL management data. This segmentation allows the system to compare values from both locations to detect whether an APL task was completed before power loss, thereby improving reliability without excessive complexity increase.
Solution Approach 2:
The patent performs a preliminary write operation to store a first value in the first location before executing the APL task. This preliminary action creates a baseline that can be compared against the second value written after task completion, enabling detection of incomplete tasks while maintaining a relatively simple memory structure.
2Reliability
If APL management data is updated in place, then the manufacturing precision is maintained, but the reliability deteriorates due to loss of task completion status information
Solution Approach 1:
The patent extracts the APL management data into two separate storage locations rather than updating in place. The first value is stored in the first location and the second updated value is stored in the second location. This extraction preserves the original data for comparison purposes, preventing information loss and enabling reliable detection of task completion status.
Solution Approach 2:
The patent creates a copy of the APL management data structure by maintaining parallel first and second locations. The second location contains a copy of the data structure with updated values after APL task execution. By comparing the first and second copies, the system can detect whether tasks were completed without overwriting the original data.
3Reliability
If checksum verification is performed without task completion detection, then the productivity is improved, but the reliability deteriorates due to use of outdated data
Solution Approach 1:
The patent performs a preliminary comparison of the first and second values immediately upon power-up, before proceeding with data reconstruction. This preliminary check ensures that the system uses the most recent valid APL management data, improving reliability without significantly impacting productivity since the comparison is a simple operation.
Solution Approach 2:
The patent implements a feedback mechanism where the comparison result of the first and second values determines whether to proceed with normal data reconstruction or to indicate an incomplete APL task. This feedback loop ensures reliable data reconstruction by preventing use of outdated information while maintaining efficient productivity through conditional processing.
Data Source
AI summary
Memory systems and devices (and associated methods) with improved active performance loss (APL) completion detection are described herein. In one embodiment, a memory device comprises nonvolatile memory and logic configured to (i) write a first value to a first location in the nonvolatile memory, (ii) detect a power loss event corresponding to the memory device, and (iii) before powering down the memory device based at least in part on the detected power loss event, write a second value to a second location in the nonvolatile memory different from the first location. The first value and/or the second value can correspond to a current power cycle number of the memory device. After power is subsequently restored to the memory device, the logic can compare the first and second values and proceed with reconstructing the memory device using APL management data when the first value matches the second value.