Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
2000-02-04
2002-02-12
Kim, Hong (Department: 2185)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C711S115000, C711S165000, C711S170000, C711S159000, C365S218000
Reexamination Certificate
active
06347355
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nonvolatile storage device, a control method of the nonvolatile storage device, and an information recording medium in which the nonvolatile storage device is realized, and more particularly to a nonvolatile storage device in which data can be written through the conversion of logical addresses to physical addresses and in which management information of the data can be recovered when data writing is interrupted, a control method for the nonvolatile storage device, and an information recording medium in which a program for controlling the nonvolatile storage device is recorded.
Further, the present invention relates to memory cards such as ATA (AT Attachment) cards, SSFDC (Solid State Floppy Disk Card Forum) cards, etc. in which data storage locations can be designated in the same way as in hard disks and floppy disks, a control method for the memory cards, and an information recording medium in which a program for controlling the memory cards is recorded.
Further, the present invention relates to a nonvolatile storage device which is provided with a flash EEPROM (Electrically Erasable Programmable Read Only Memory) and a RAM (Random Access Memory), in which a translation table for translating logical addresses designated as requested to read and write data into physical addresses in the flash EEPROM is divided and stored in the flash EEPROM and the RAM, and in which the translation table is prepared in the RAM based on the data of the translation table stored in the flash EEPROM, a control method for the nonvolatile storage device, and an information recording medium in which a program for controlling the nonvolatile storage device is recorded.
2. Description of the Related Art
Memory cards such as ATA cards, SSFDC cards, etc., as nonvolatile storage devices, are becoming wide spread as external storage devices of computers, and standardization of their specifications is in progress.
In particular, memory cards according to the PC (Personal Computer) card standard or the PCMCIA (Personal Computer Memory Card International Association) standard operate as an external storage device when they are connected to their host computers, and when the memory cards are disconnected from their host computers, they can be moved and carried alone with the data stored therein. Even if their host computers are powered on, hot connection and disconnection are possible. Because of such advantages, memory cards such as ATA cards, etc. are widely used as a means to record photograph data taken by digital cameras, etc. and to transfer the data to their host computers.
When memory cards such as ATA cards, SSFDC cards, etc. are requested to write and read data by their host computers to which the memory cards are connected, it is required to designate storage locations for the data. When the storage locations are designated, integers called logical addresses are used. Logical addresses are also used to designate storage locations when writing to and reading from hard disks and floppy disks are performed. Further, there are cases where the logical addresses are called logical block addresses.
For example, in accessing hard disks, as high-speed processing is possible when a certain amount of data such as 512 bytes of data are handled together, writing and reading are performed in units of a sector containing 512 bytes. Storage locations in actual hard disks are designated by a cylinder number, head number, sector number, etc., but in order to standardize the processing of reading and writing, the storage areas of hard disks are virtually arranged in a straight line and divided in sector units from the beginning, and they are numbered. These numbers mean logical addresses. In the case of floppy disks, logical addresses can be defined in the same way.
In host computers, logical addresses are used to access hard disks, etc., and therefore, when such a designating method of storage locations is made available to memory cards such as ATA cards, SSFDC cards, etc., it is useful in development of applications and data management. Therefore, in such memory cards, control is required so as to be able to designate storage locations using logical addresses.
Further, also when memory cards are connected to the above-mentioned digital cameras, logical addresses are used to designate storage locations in order that the digital cameras request the memory cards to write and read data. That is, the digital cameras operate as the above-mentioned host computer.
Now, such memory cards are realized because of nonvolatile storage devices, flash EEPROMs in particular, contained therein. The storage area of the flash EEPROMs is divided into one or a plurality of blocks, each block is divided into one or a plurality of pages, and each page is composed of a storage area in which the same capacity as a unit in writing and reading from hard disks, etc., for example, 512 bytes, can be stored. Further, a type in which an additional redundant area, for example, a storage area of 16 bytes, is added on each page is also widely used. The former has a capacity of 512 bytes in one page and the latter has a capacity of 528 bytes in one page, but it is common to both that the same 512 bytes of data, as a unit in reading and writing by host computers, can be stored.
Locations of the storage areas in flash EEPROMs can be uniquely identified by designating a chip number, block number in the chip, and page number in the block. Then, the storage areas in the flash EEPROMs are virtually arranged in a straight line and each page is sequentially numbered in units of pages from the beginning. These numbers are called physical addresses. That is, the locations in the storage areas in the flash EEPROMs can be designated by the physical addresses.
SUMMARY OF THE INVENTION
Flash EEPROMs are read-only memories which can be electrically erasable. That is, in principle, data can be written only once on electrically erased pages. Therefore, when it is required to change data stored on a certain page, firstly the page is erased and then new data are required to be written. Further, in flash EEPROMs, in order to decrease the number of elements and perform high-speed processing, the above-mentioned erasure is technically characterized in that it is carried out in units of block.
Further, some flash EEPROMs have a function of overwriting on their pages which already have data written thereon, on the redundant portions in particular. However, regarding such an overwriting function, the number of times of overwriting is limited in most cases. Further, there are also many flash EEPROMs which do not have the function of overwriting.
In such memory cards, by converting the logical addresses designated by their host computers into physical addresses, writing and reading from the pages located at the physical addresses are performed. However, because the writing is limited as described above, it is highly possible that the correspondence between the logical addresses and the physical addresses be frequently changed.
Up to now, a method of storing management information for making logical addresses correspond to physical addresses also in flash EEPROMs has been known. Further, in order to speed up reading and writing, a method which is provided for RAMs besides flash EEPROMs, in which an address translation table for translating logical addresses into physical addresses is stored, and in which when the correspondence between the logical addresses and the physical addresses is updated, the address translation table stored in the RAMs is also updated, has been proposed.
In such memory cards, memory cards according to the PC card standard in particular, hot unplugging is possible only when the writing process is not being performed, but there are cases where the memory cards are mistakenly pulled out by the user while the writing process is being performed. Further, when the memory cards are used as a storage device of digital cameras, etc., there are cases where power is turned of
Kimura Tsunenori
Kondo Yoshimasa
Kim Hong
Seiko Epson Corporation
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