Flash Memory Last Written Page Indicator Circuit
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Solution Overview
Problem
Current methods for determining the last written page in flash memory are time-consuming and bandwidth-intensive, leading to poor system performance during power-up and data transfer between the controller and flash memory.
Innovation Solution
Implementing a flash memory device with a control circuit that uses signal level measurements and comparisons with predetermined threshold values to identify an erased page within a block, allowing the flash memory to internally determine the last written page address and communicate it to the controller, thereby reducing data transfer and improving system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the controller determines whether a page is erased by reading and counting 1's or 0xFF patterns, then the page status can be accurately determined, but the data transfer time and channel bandwidth consumption increase significantly
Solution Approach 1:
The patent extracts only the necessary information (erased page indicator) from the flash memory block rather than transferring entire page data. The controller sends a read command and receives only a small indicator signal that identifies which pages are erased, eliminating the need to transfer large amounts of page data while maintaining accurate page status determination.
Solution Approach 2:
Instead of reading and analyzing complete page data to determine erased status, the patent uses a partial action approach where only a minimal indicator is read. This indicator contains just enough information to identify erased pages without requiring full page data transfer, thus reducing time and bandwidth while preserving measurement accuracy.
2Reliability
If sequential page-by-page reading is performed to find an erased page, then all pages can be checked thoroughly, but the process becomes time-consuming and bandwidth-intensive
Solution Approach 1:
The patent extracts erased page status information in a condensed form (indicator signal) rather than transferring complete page data. This allows the system to verify the status of multiple pages simultaneously through a single read operation, maintaining reliability while dramatically improving productivity by eliminating sequential data transfer.
Solution Approach 2:
The flash memory performs preliminary processing internally to prepare the erased page indicator before data transfer. This preliminary action consolidates the status of multiple pages into a single indicator that can be read quickly, ensuring complete page status verification while accelerating the overall process by avoiding sequential reading.
3Speed
If binary search algorithm is used to locate an available page, then the search process is faster than sequential search, but channel bandwidth and power consumption increase
Solution Approach 1:
The patent extracts erased page information in a compact indicator format that enables direct identification of available pages. This approach achieves fast page location similar to binary search but with minimal bandwidth consumption because only a small indicator is transferred rather than large amounts of page data being read and processed.
Solution Approach 2:
The flash memory performs self-service by internally generating and providing the erased page indicator without requiring the controller to read and analyze complete page data. This self-service mechanism achieves fast page location while minimizing channel bandwidth usage and power consumption, as the heavy lifting is done internally within the flash memory device.
Data Source
AI summary
A flash memory device includes a flash memory having a plurality of blocks, each block having a plurality of pages, and a control circuit configured to receive a command, decode the received command to determine whether the command is a last written page command, upon determining that the command is the last written page command, select a block of the plurality of blocks, and perform a number of iterations. Each of the iterations includes obtain a measurement of a signal level of a page in the selected block, compare the signal level with a predetermined threshold value, determine whether the page is an erased page based on a comparison result, upon determining that the page is an erased page, save an address associated with the erased page and output the address of the erased page, and upon determining that the page is not an erase page, perform a next iteration.