File Allocation Table Management for Nonvolatile Memory Compatibility

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Solution Overview

Problem

One-time or few-time programmable non-volatile memory technologies are not compatible with existing consumer electronic devices that use erasable, re-programmable flash memory, requiring firmware upgrades or limiting market compatibility.

Innovation Solution

A controller allocates clusters from one end of the address range, while the host allocates from the other end, with allocation information recorded in volatile memory to update the File Allocation Table (FAT) in non-volatile memory, allowing backwards compatibility without firmware updates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If one-time or few-time programmable memory is used, then cost is reduced and compatibility with existing devices is improved, but the ability to update file system firmware is lost

Engineering Contradiction:

Improvecompatibility with existing devicesVSAvoidfirmware update capability

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent introduces a file allocation table (FAT) stored in non-volatile memory as an intermediary structure that enables the memory device to present a standard FAT file system interface to hosts. This FAT acts as a mediator between the OTP/FTP memory constraints and the host's expectations, allowing compatibility without requiring firmware updates in the host device.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the file system functionality by separating the FAT storage from the data storage areas. The FAT is stored in a dedicated portion of non-volatile memory, while data is stored in other portions. This segmentation allows the FAT to be managed independently and enables the memory to emulate a standard FAT file system despite the OTP/FTP constraints.

Inventive Principle:

Principle #1Segmentation

2Productivity

If clusters are allocated by both host and controller, then memory utilization is improved, but FAT synchronization complexity increases

Engineering Contradiction:

Improvememory utilizationVSAvoidFAT synchronization

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent implements a self-service mechanism where the controller automatically updates the FAT to reflect its own cluster allocations. When the controller allocates clusters from the other end of the address range, it autonomously modifies the FAT entries without requiring host intervention, thereby maintaining FAT synchronization while enabling dual allocation.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent establishes a feedback loop where the controller monitors its own cluster allocations and automatically updates the FAT accordingly. This feedback mechanism ensures that the FAT accurately reflects the current state of cluster allocation by both host and controller, maintaining synchronization without manual intervention.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS7681008B2Systems for managing file allocation table information

Publication Date: 2010.03.16 SANDISK TECHNOLOGIES LLC

AI summary

In a nonvolatile memory system, a host allocates clusters and records allocation information in a File Allocation Table that is stored in the nonvolatile memory. A controller separately allocates certain data and records allocation in a record in a volatile memory. File Allocation Table information provided to the host is modified according to the record in the volatile memory.