Static information storage and retrieval – Floating gate – Particular biasing
Reexamination Certificate
1999-01-19
2001-05-01
Nelms, David (Department: 2818)
Static information storage and retrieval
Floating gate
Particular biasing
C365S052000, C365S185120
Reexamination Certificate
active
06226202
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a flash memory card having a flash memory mounted on a card as a memory medium.
Attention has been paid to flash memories (flash EEPROMS) as semiconductor memories that will replace magnetic disks such as hard disks and floppy disks. A flash memory is a nonvolatile, low-power-consumption semiconductor memory which can be electrically reprogrammed. Since these memories are compact, lightweight, and highly resistant to vibrations, the application range of the memories in portable devices and the like extends.
Such flash memories find a typical application in flash memory cards. A flash memory card is a card obtained by mounting one or a plurality of flash memories (IC chips) on one card. This card is generally provided as a PC card complying with PCMCIA.
A PC card needs to have card attribute information referred to as CIS (Card Information Structure) information that displays or describes the configuration of the card, the manner of accessing the card, and the like, owing to the PCMCIA requirements (specifications) that the compatibility of the card should be improved between host computers (e.g., personal computers) complying with the standards.
On a flash memory card of this type, the following components are mounted, in addition to a flash memory: a controller connected to a host system through a predetermined interface to execute data read/write operations with respect to the flash memory on the card; a ROM which holds programs required for the operation of the controller and a RAM for holding data; and the like.
In a conventional flash memory card of this type, CIS information is stored in the ROM on the card, together with other software programs. When the flash memory card is inserted into the card slot of the host system, the host computer searches for the CIS information of this flash memory card. In the flash memory card, the controller reads out the CIS information from the ROM and sets it in the RAM or register that the host computer can directly access. The host computer assigns a memory space, an I/O space area, an interruption level, and the like to the card on the basis of the CIS information loaded from the flash memory card, and sequentially read/write-accesses the flash memory on the card afterward.
In some case, part or all of the CIS information of the flash memory card must be rewritten. When, for example, flash memory cards manufactured by a card maker as a primary supplier are to be distributed as cards provided a card vendor as a secondary supplier, pieces of attribute information such as product maker information, product name information, and product version of the CIS information of each card need to be updated.
In a conventional flash memory card, however, since the CIS information is stored as fixed information in the ROM as described above, it is practically impossible to rewrite the CIS information.
Note that the conventional flash memory card does not have the function of protecting the data stored in the flash memory, i.e., the write protect function of inhibiting new data from being written in the flash memory. For this reason, new data may be overwritten in the flash memory card in which data to be retained is stored. As a result, the important data may be erased.
Further, in a flash memory card wherein a flash memory unit is detachable to an adapter, the contents of CIS must be changed in accordance with the flash memory body.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a flash memory card which allows card attribute information to be arbitrarily rewritten without increasing the number of parts and the cost.
It is another object of the present invention to provide a flash memory card which can reliably retain stored data by preventing an undesired write operation.
According to the first aspect of the present invention, there is provided a flash memory card comprising one or a plurality of flash memories and a controller having an interface connected to a host computer and designed to store card attribute information to be presented to the host computer at a predetermined position in the flash memory.
In the above flash memory card, the storage area of each flash memory is divided into a predetermined number of blocks, and the card attribute information is stored in a normal block having the highest or lowest address rank in the flash memory in which the card attribute information is to be stored.
In addition, in the above flash memory card, each block is divided into a predetermined number of pages. Every time the card attribute information stored in the block is updated partly or totally, new card attribute information is sequentially written in the page having the next address.
Furthermore, in the above flash memory card, pieces of identical card attribute information are redundantly stored at different storage positions in a predetermined flash memory in which the card attribute information is to be stored.
According to the second aspect of the present invention, there is provided a flash memory card comprising one or a plurality of flash memories, an interface which can be connected to a host computer, and a write protect circuit for inhibiting the host computer from writing data in the flash memories.
The flash memory card according to the second aspect further comprises an error processor for detecting and correcting an error in data read out from an arbitrary position in the flash memory in accordance with a read request from the host computer, and a data transfer section for, when an error is detected by the error processor, writing the readout data, corrected by the error processor, in another available storage position regardless of whether the write protect circuit is set in a write disable state.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
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Auduong Gene N.
Nelms David
Pillsbury Madison & Sutro LLP
Tokyo Electron Device Limited
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