Nonvolatile Memory Protection Mode via SLC MLC Read Method Switching
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Solution Overview
Problem
Existing nonvolatile memory devices lack an effective mechanism to prevent data leakage when entering a protection mode without erasing stored data, as they cannot differentiate between normal and protected data modes efficiently.
Innovation Solution
A nonvolatile memory device is designed with divided multi-level cell (MLC) and single level cell (SLC) regions, where data is read using the SLC method in the MLC region and the MLC method in the SLC region when the protection mode is activated, ensuring that normal data is not accessible upon entry into the protection mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If data is not erased before entering protection mode, then the time to enter protection mode is reduced, but data leakage risk increases
Solution Approach 1:
The memory device is divided into multiple memory blocks that can be independently managed. When protection mode is activated, only specific memory blocks are locked while others remain accessible, allowing selective data protection without erasing entire memory regions. This segmentation enables faster entry into protection mode by targeting only necessary blocks.
Solution Approach 2:
Different memory blocks are assigned different access permissions and protection levels. The controller applies protection selectively to specific blocks containing sensitive data, while maintaining normal access to other blocks. This local differentiation allows the system to enter protection mode quickly for critical data without compromising overall system functionality.
2Device complexity
If the memory device uses a single read method, then the device complexity is reduced, but the ability to prevent data leakage in protection mode is insufficient
Solution Approach 1:
The memory device dynamically switches between SLC and MLC read methods based on the activation state of protection mode and the target memory block. In normal mode, the device uses standard read methods for each block type. When protection mode is activated, it switches to alternative read methods that produce unreadable or incorrect data outputs, preventing data leakage without requiring additional hardware components.
Solution Approach 2:
The device changes operational parameters (read voltage levels, pulse sequences, or decoding methods) depending on the protection mode state. By modifying these parameters, the same physical memory structure can operate in different modes: normal read mode for data access and protection mode for data concealment, eliminating the need for separate hardware structures.
3Reliability
If the memory device supports both SLC and MLC methods, then data protection capability is improved, but the device complexity increases
Solution Approach 1:
The memory device integrates both SLC and MLC read capabilities within a single unified architecture. The same memory blocks can be read using different methods depending on the protection mode requirement. This multi-functionality allows the device to maintain data protection capabilities while avoiding the need for completely separate hardware structures for each read method.
Solution Approach 2:
The device uses the existing memory cell structure and read circuitry to implement multiple read methods by applying different voltage sequences or decoding schemes. Rather than creating duplicate hardware structures, the system creates virtual copies of read operations through software-controlled parameter variations, reducing hardware complexity while maintaining protection capabilities.
Data Source
AI summary
A nonvolatile memory device comprising: a first block comprising multiple single level cells (SLCs), a second block comprising multiple multi-level cells (MLCs), and an operation controller is suitable to perform, in response to a read command applied from an outside: a read operation using an SLC method on first data stored in the first block or a read operation using an MLC method on second data stored in the second block in a normal mode, and a read operation using the MLC method on the first data or a read operation using the SLC method on the second data in a protection mode.