Flash Memory Read Operation Using Dummy Data Programming
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Solution Overview
Problem
Flash memory devices with multi-level cells face challenges in performing read operations due to the reliance on flag cells for program state information, which can lead to increased complexity, reduced storage capacity, and longer read times, especially as the number of bits stored increases.
Innovation Solution
A flash memory device and method that eliminates the need for flag cells by performing a dummy data program operation to ensure all pages are programmed before executing a read command, using a controller to generate and store dummy data and program it to redundant pages, allowing for read operations without relying on flag cell program state information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flag cells are used to indicate program state in MLC flash memory, then program state information can be tracked, but chip size increases and storage capacity decreases
Solution Approach 1:
The patent removes the flag cell structure from the memory architecture entirely. Instead of using dedicated flag cells to indicate program state, the system uses the main data pages themselves to store and track program state information through a dummy data program operation, thereby eliminating the extra hardware overhead and reducing chip size.
Solution Approach 2:
The patent makes the data pages multi-functional by using them both for storing user data and for indicating program state. The dummy data program operation transforms ordinary data pages into state indicators, eliminating the need for separate flag cells and increasing effective storage capacity.
2Reliability
If flag cells are used to indicate program state in MLC flash memory, then program state information can be tracked, but device complexity increases
Solution Approach 1:
The patent extracts and removes the flag cell component from the memory system, simplifying the overall device architecture. The program state tracking function is redistributed to existing data pages through a control logic mechanism, reducing structural complexity.
Solution Approach 2:
Instead of using special flag cells to indicate program state, the patent inverts the approach by using the data pages themselves (with dummy data) to indicate the state. This inversion simplifies the hardware structure while maintaining the state tracking function.
3Reliability
If flag cells are used to indicate program state in MLC flash memory, then program state information can be tracked, but read operation time increases
Solution Approach 1:
The patent performs a dummy data program operation in advance before the actual read operation. This preliminary action ensures that all pages are in a programmed state, eliminating the need for runtime flag cell checks and reducing read operation time.
Solution Approach 2:
The patent maintains continuous useful action by using the dummy data program operation to prepare the memory state in advance. This ensures that the subsequent read operation can proceed without interruption or additional state verification steps, improving read speed.
Data Source
AI summary
A method of performing a read operation in a flash memory device is disclosed. The flash memory has a memory cell array including at least one block, the block having a plurality of pages. The method comprises receiving a read command to read data from a selected page in the block; determining whether or not the block has any page that has not been programmed; performing a dummy data program operation on at least one page that is determined not to have been programmed; and executing the read command to read the data of the selected page after the dummy data program operation is completed.