CN102945274A - File system FAT (file allocation table) partition table management method based on NOR FLASH - Google Patents

Abstract

The invention provides a file system FAT (file allocation table) partition table management method based on NOR FLASH, which is characterized in that a region in NOR FLASH is allocated and is used as an FAT partition table management region, the region is further divided into two parts, i.e. an FAT partition table index region and an FAT partition table region, wherein the FAT partition table region can be used for storing a plurality of FAT partition tables, firstly the region in the NOR FLASH is allocated and is used as the FAT partition table management region, the FAT partition table management region comprises the FAT partition table index region and a plurality of FAT partition tables, a current valid FAT partition table is obtained according to an index number in the FAT partition table index region, the FAT partition table next to the current valid FAT partition table is only required to be erased when the FAT partition table is required to be modified for file operation, and index numbers in the FAT partition table index region are cyclically increased.

Description

A kind of management method based on NOR FLASH file system FAT partition table

Technical field

The present invention relates to the built-in terminal field, be specifically related to a kind of management method based on NOR Flash File System FAT partition table.

Technical background

Development along with the built-in terminal technology, diversified application constantly occurs, and most application all is accompanied by processing and the storage of mass data, embedded storage generally can adopt NOR Flash as storage medium, traditional data storage method is to specify Flash start address and length, and the length of appointment must be the multiple of Flash erasable block size, avoids occurring on the erasable block that several data appears at a Flash, thereby can avoid the destroyed danger of data.Specify the method for Flash start address and length, two shortcomings are arranged: the first, the data expansion is dumb, if there is new application to occur, needs to preserve the new data of using, and must again distribute a zone for new data in program; The second, waste Flash space, NOR Flash erasable block is generally 64K, only has the seldom data of byte for a class, also needs to distribute the space of 64K, can cause like this waste in Flash space.File system administration data storage can flexible expansion, and new application has been arranged, and only needs reading and writing of files to get final product, and file system is take bunch as least unit in addition, and cluster is generally 4K or 8K, has greatly reduced the waste in Flash space.Therefore, it is imperative to manage NOR FLASH storage medium with file system.Yet traditional file system only has a single FAT partition table, partition table is modified on original partition table basis and directly makes amendment, this mode is not suitable for NOR FLASH storage medium, because the characteristic of NOR FLASH need at first be wiped whole, and then write, if system power failure in erase process, whole partition table loss of data and irrecoverable.Consider the characteristic of NOR FLASH, also have higher requirement for file system, mainly comprise the security of file system, reliability and erasable balance.

In view of the traditional shortcoming of file system FAT partition table management method on NOR FLASH storage medium application, need the management method that proposes a kind of new FAT partition table based on NOR FLASH storage medium badly, to satisfy the security of file system, reliability and erasable balance, thus the present invention to propose a kind of management method based on NOR FLASH file system FAT partition table just necessary.

Summary of the invention

The purpose of this invention is to provide a kind of management method based on NOR FLASH file system FAT partition table.

Purpose among the present invention realizes in the following manner, in NOR FLASH, distribute a regional FAT partition table directorial area, be divided into again two parts in this zone: FAT partition table index area and FAT partition table district, wherein a plurality of FAT partition tables can be deposited by FAT partition table district, at first in NOR FLASH flash memory, distribute a regional FAT partition table directorial area, FAT partition table directorial area comprises FAT partition table index area and a plurality of FAT partition table, current effective FAT partition table obtains according to the call number in the FAT partition table index area, when file operation is arranged, when needing to revise the FAT partition table, the next FAT partition table that only needs erasable current effective FAT partition table, simultaneously, the call number circulation increases progressively in the FAT partition table index area;

The management process of FAT partition table is as follows:

Use a FAT partition table index area and a plurality of FAT partition table, consider the erasing and writing life of NOR FLASH, a plurality of call numbers are deposited in the index area, adopt the method for increment storage to manage, each call number takies 4 bytes of storage space, wherein 2 bytes effectively identify, 2 byte index number, call number is designated effectively with 0xaaaa, sequential search in the index area, the call number of finding last 0xaaaa sign is current effective call number, whole index area is full, wipe whole index area, and the current cable quotation marks are written to again first position of index area, restart the increment storage, adopt a plurality of FAT partition table designs, can play the effect of backup, when the FAT partition table is revised, only wipe a FAT partition table and write, other partition tables are not done change, have strengthened the safety and reliability of file system, and simultaneously a plurality of FAT partition table circulations are erasable, accomplished to greatest extent the erasable balance of file system FAT partition table, prolonged the serviceable life of NOR FLASH, a plurality of FAT partition tables use FAT partition table call numbers to manage, can be convenient, flexible navigate to current effective FAT partition table position.

The invention has the beneficial effects as follows: based on the application of built-in terminal NOR FLASH file system, can strengthen the safety and reliability of file system, under the unexpected power-down conditions of built-in terminal, avoid occurring the destroyed situation of file system, also effectively realized in addition the erasable balance of file system, prolonged the serviceable life of NOR FLASH, made it more be applicable to diversified built-in terminal product, thereby have boundless development space.Use FAT partition table call number to manage a plurality of FAT partition tables, can play the effect of FAT partition table backup, an erasable FAT partition table only when the FAT partition table is revised, other partition tables are not done change, strengthened the safety and reliability of file system, simultaneously a plurality of FAT partition tables circulations are erasable, and the erasable balance of having accomplished to greatest extent file system FAT partition table has prolonged serviceable life of NOR FLASH.

Description of drawings

Fig. 1 is FAT partition table directorial area synoptic diagram;

Fig. 2 is FAT partition table index area increment storage synoptic diagram.

Embodiment

With reference to accompanying drawing method of the present invention is done detailed description:

As described in the summary of the invention, the management method of the NOR FLASH file system FAT partition table of mentioning among the present invention, in NOR FLASH, to distribute a regional FAT partition table directorial area, be divided into again two parts in this zone: FAT partition table index area and FAT partition table district, wherein a plurality of FAT partition tables can be deposited by FAT partition table district, referring to accompanying drawing 1 and accompanying drawing 2.At first, create the initial file system partition table in FAT partition table 0 position, it is effective partition table that while starting position, index area writes 4 byte 0xaaaa0000 sign FAT partition table 0.Secondly, when file operation is arranged, FAT partition table content changes, need to write NOR FLASH storage medium, the FAT partition table that changes no longer writes FAT partition table 0 position, but write FAT partition table 1 position, write finish after, it is effective partition table that the 5th byte location in FAT partition table index area begins to write 4 byte 0xaaaa0001 sign FAT partition table 1.By that analogy.Again, if current FAT partition table n is last partition table of FAT partition table district, then next FAT partition table writes FAT partition table 0 position, and the index area writes 4 byte 0xaaaa0000 simultaneously, and circulation is deposited.At last, if the index area increment write fullly, then deposit call number next time, need at first wipe whole index area, then write current effective call number in the starting position, index area.

Traditional file system FAT partition table management method is not suitable for NOR FLASH storage medium, among the present invention based on the management method of NOR FLASH file system FAT partition table, take into full account the erasable characteristic of NOR FALSH storage medium, can to satisfy effectively NOR FLASH file system security, the needs of reliability and erasable balance.

Claims (1)

1. management method based on the file system FAT partition table of NOR Flash, it is characterized in that, in NOR FLASH, distribute a regional FAT partition table directorial area, be divided into again two parts in this zone: FAT partition table index area and FAT partition table district, wherein a plurality of FAT partition tables can be deposited by FAT partition table district, at first in NOR FLASH flash memory, distribute a regional FAT partition table directorial area, FAT partition table directorial area comprises FAT partition table index area and a plurality of FAT partition table, current effective FAT partition table obtains according to the call number in the FAT partition table index area, when file operation is arranged, when needing to revise the FAT partition table, the next FAT partition table that only needs erasable current effective FAT partition table, simultaneously, the call number circulation increases progressively in the FAT partition table index area;

The management process of FAT partition table is as follows:

Use a FAT partition table index area and a plurality of FAT partition table, consider the erasing and writing life of NOR FLASH, a plurality of call numbers are deposited in the index area, adopt the method for increment storage to manage, each call number takies 4 bytes of storage space, wherein 2 bytes effectively identify, 2 byte index number, call number is designated effectively with 0xaaaa, sequential search in the index area, the call number of finding last 0xaaaa sign is current effective call number, whole index area is full, wipe whole index area, and the current cable quotation marks are written to again first position of index area, restart the increment storage, adopt a plurality of FAT partition table designs, can play the effect of backup, when the FAT partition table is revised, only wipe a FAT partition table and write, other partition tables are not done change, have strengthened the safety and reliability of file system, and simultaneously a plurality of FAT partition table circulations are erasable, accomplished to greatest extent the erasable balance of file system FAT partition table, prolonged the serviceable life of NOR FLASH, a plurality of FAT partition tables use FAT partition table call numbers to manage, can be convenient, flexible navigate to current effective FAT partition table position.

Images