NAND Flash Sequential Read Cycle Merging
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Solution Overview
Problem
Current NAND flash memory systems face inefficiencies in read operations, particularly when handling sequential data, as they often require separate read cycles for each page, leading to increased power consumption and reduced performance.
Innovation Solution
Implementing a method to combine read cycles for multiple pages stored in the same group of memory cells, utilizing a single read cycle to sense data from multiple levels, thereby reducing overhead phases such as epilogue, wordline ramp, and read recovery phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate read cycles are used for each page in NAND flash memory, then data can be read accurately from each page, but power consumption increases and read performance decreases
Solution Approach 1:
The patent combines multiple separate read cycles into a single unified read cycle by merging the read commands for multiple pages. The controller issues a single read command that specifies multiple logical page addresses, and the NAND flash memory device returns all requested pages in one operation. This merging eliminates redundant overhead phases (epilogue, wordline ramp, read recovery) that would otherwise occur separately for each page, thereby reducing power consumption while maintaining data reading accuracy.
2Ease of operation
If separate read cycles are used for each page in NAND flash memory, then each page can be read individually, but read performance and efficiency are reduced
Solution Approach 1:
The patent merges multiple individual page read operations into a single combined read operation. The controller constructs a unified read command that includes multiple logical page addresses, and the memory device processes all pages in one go. This approach maintains the capability to read individual pages selectively while dramatically improving read performance by eliminating the sequential execution overhead of multiple separate read cycles.
3Reliability
If multiple overhead phases (epilogue, wordline ramp, read recovery) are executed for each page read, then proper memory operations are ensured, but time is lost and efficiency is reduced
Solution Approach 1:
The patent combines the overhead phases of multiple read operations into a single set of overhead phases executed once for the entire batch of pages. The epilogue phase, wordline ramp phase, and read recovery phase are performed collectively for all requested pages rather than repeating them for each individual page. This merging maintains proper memory operation correctness while reducing the total time lost to overhead by a factor proportional to the number of pages read in the combined operation.
Data Source
AI summary
In one embodiment, an apparatus comprises a storage device comprising a NAND flash memory. The storage device is to receive a read request from a computing host; identify a plurality of pages specified by the read request that are stored in the same group of memory cells of the NAND flash memory, wherein each memory cell of the group of memory cells is to store a bit of each of the plurality of identified pages; and read, in a single read cycle, the plurality of pages from the group of memory cells of the NAND flash memory.