Electrical computers and digital processing systems: memory – Storage accessing and control – Control technique
Reexamination Certificate
1998-09-28
2001-04-17
Thai, Tuan V. (Department: 2186)
Electrical computers and digital processing systems: memory
Storage accessing and control
Control technique
C711S103000, C711S145000, C714S006130
Reexamination Certificate
active
06219768
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a storage device for storage of optional data, data management information for controlling this optional data and the area management information for supervising the state of the area in which to store the data, and to a data processing system employing this storage device. The invention also relates to a data writing and readout method for writing or reading out the optional data, data management information for controlling this optional data and the area management information for supervising the state of the area in which to store the data, into or from the storage device.
2. Description of the Related Art
Up to now, a card type external storage device, referred to hereinafter as a memory card, employing a flash memory (electrically erasable programmable read-only memory (ROM)) as a recording medium, has been proposed as an external data storage device used for an electronic equipment.
In this memory card, optional data and the management information as ancillary data are stored in a memory as a storage medium. When these data and the management information are sent from the memory card to e.g., a host side computer, the data or the management information is corrected for errors, using the error correction codes, to correct the data for errors produced by cell malfunctions before outputting the data or information.
As the above management information, the information for management of the state of an area for data storage (area management information), such as the information specifying whether or not the area holding the data on memory is usable, is occasionally stored, in addition to the data-dependent information for supervising the data (data management information), such as logical addresses indicating the sequence of the stored data.
Since the area management information is the information concerning an in-memory area, that is information independent of data, there may arise the necessity of rewriting the information after storage of the data, and hence the area management information is usually adapted to be rewritten by itself without rewriting the data.
Also, if an error is produced in the area management information, and a usual error correction code is used to correct the information for errors, the error correction codes need to be rewritten every time the information is rewritten. Thus, for the area management information, the same information is desirably distributed in plural bits and stored in this state in order to combat errors without employing the error correction code for error correction.
However, if the area management information is distributed in plural bits and stored in this state, transmission data is increased in length when reading out data from the memory card, thus deteriorating the transmission efficiency. Recently, there has been proposed a technique of storing the information of plural bits in a single cell. If the number of bits stored in a cell is increased, it becomes necessary to increase the number of distributed bits for combatting errors thus further deteriorating the transmission efficiency.
Also, if the cell structure of the memory card is changed, such that the manner of information distribution is changed, it becomes necessary to change the configuration of data sent from the host side to the memory card, the structure of a driver for the host side to manage the memory of the memory card or the interface specifications need to be changed to render compatibility with the existing memory card difficult. In particular, in the case of the electronic equipment having a built-in driver, such as a digital camera, new memory cards cannot be used because software version upgrading measures cannot be used.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a storage device, a data processing system and a data writing and readout method whereby the area management information can be distributed and stored without deteriorating the transmission efficiency and compatibility with the pre-existing storage devices can be achieved even if the cell structure is changed.
In one aspect, the present invention provides a storage device including storage means for storing data and the area management information for supervising the state of an area for storing the data, conversion means for converting the input area management information into an area management flag corresponding to the area management information and redundant data appended thereto or converting the area management flag read out from the storage means back into the original area management information, and control means for writing the area management flag converted by the conversion means in storage means or reading out the area management flag from the storage means to send the read-out flag to the conversion means to output the original area management information converted by the conversion means.
With this storage device, the input area management information is converted by conversion means into an area management flag having the number of bits larger than the area management information. The area management flag converted by the conversion means is written by the control means in the storage means.
With the present storage device, the area management flag read out from the storage means by the control means is converted by conversion means into the original area management information. The area management information thus converted by the conversion means is outputted under control by control means.
With the present storage device, the conversion means preferably includes a conversion table in which the area management information and the area management flag are recorded in association with each other. The conversion means converts the input area management information into the area management flag by having reference to the conversion table.
With the present storage device, the conversion means preferably includes a flag discrimination circuit for discriminating the original area management information from a pattern of the area management flag read out from the management information storage area of the storage means. In this case, the conversion means converts the area management flag read out from the storage means to the original area management information.
In another aspect, the present invention provides a data processing system including a storage device for storing data and the area management information for supervising the state of an area for storing the data, and a data processing device for sending the data and the area management information to the storage device or processing the data supplied from the storage device and the area management information. The, storage device converts the area management information supplied from the data processing device into an area management flag corresponding to this area management information having appended redundant data. The storage device also converts the stored area management flag to the original area management information to supply the original area management information to the data processing device.
Preferably, the storage device has a conversion table in which the area management information and the area management flag are recorded in association with each other and the input area management information is converted into the area management flag by having reference to the conversion table.
Preferably, the storage device has a flag discrimination circuit for discriminating the original area management information from a pattern of the stored area management flag and the stored area management flag is converted into the area management information using this flag discrimination circuit.
Preferably, the storage device has a flash memory and the storage device converts the area management information into an area management flag of at least three bits per bit of the information, distributes the flag in at least three cells of flash memory and stores the flag in this distributed state in the cell
Hirabayashi Mitsuhiro
Nakanishi Kenichi
Sassa Akira
Frommer William S.
Frommer Lawrence & Haug LLP.
Kessler Gordon
Sony Corporation
Thai Tuan V.
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