Electrical computers and digital processing systems: memory – Address formation – Address mapping
Reexamination Certificate
1998-11-12
2001-08-28
Gossage, Glenn (Department: 2187)
Electrical computers and digital processing systems: memory
Address formation
Address mapping
C711S103000, C711S206000, C713S002000
Reexamination Certificate
active
06282624
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a non-volatile memory apparatus, a method for controlling a non-volatile memory apparatus, and a data storage medium that stores a program for controlling a non-volatile memory apparatus. More particularly, the present invention relates to a non-volatile memory apparatus that is capable of writing and reading data by designating a logic sector address thereof and has a relatively short preparation time between the time power is turned on and the time reading and writing operations can be performed, a method for controlling such a non-volatile memory apparatus and a data storage medium storing a program for controlling such non-volatile memory apparatus.
Also, the present invention relates to memory cards such as ATA (AT Attachment) cards, SSFDC (Solid State Floppy Disk Card forum) cards, and the like in which locations to store data are designated by a designation method similar to that used for hard disks and floppy disks, a method for controlling the memory cards, and a data storage medium that stores a program to control the memory cards.
Furthermore, the present invention relates to a non-volatile memory apparatus having a flash EEPROM (Electrically Erasable Programmable Read Only Memory) and a RAM (Random Access Memory). In one aspect, conversion tables for converting logic sector addresses (that are designated upon data reading and data writing) into physical page addresses in the flash EEPROM are divided and stored in the flash EEPROM and the RAM. The present invention also relates to a method for controlling the non-volatile memory apparatus, and a data storage medium that stores a program to control the non-volatile memory apparatus.
Moreover, the present invention relates to a non-volatile memory apparatus that renews an address conversion table that is stored in a flash EEPROM in units of pages, and manages data to be stored in a flash EEPROM (including data sent from a host computer for reading and writing, as well as data for an address conversion table) in units of blocks each containing a plurality of pages, a method for controlling the non-volatile memory apparatus and a data storage medium that stores a program for controlling the non-volatile memory apparatus.
2. Description of Related Art
Memory cards such as ATA cards and SSFDC cards that are non-volatile memory apparatuses are becoming popular as external memory apparatuses for computers, and standardization of their specification is in progress.
In particular, a memory card according to the PC (Personal Computer) card standard or the PCMCIA (Personal Computer Memory Card International Association) standard operates as an external memory apparatus when connected to a host computer. When removed from the host computer, the memory card can be transferred or transported as a stand-alone unit while maintaining stored data. Even when the host computer is powered on, hot insertions and removals of the memory card can be performed. Because of these advantages, memory cards such as ATA cards are widely used, for example, as means for storing photographic data taken by a digital camera and transferring the data to a host computer.
When the host computer sends a request for writing data in or reading data from a memory card, such as an ATA card or an SSFDC card, an address that stores the data needs to be designated. When the storage location is designated, a set of integers called a logic sector address is used. Logic sector addresses are also used to designate data storage locations when data are read from or written in a hard disk or a floppy disk. A logic sector address is also called as a logic block address.
For example, for accessing a hard disk, a high speed processing can be achieved when data of a relatively large size, for example, 512 bytes of data is processed in one lot. Therefore, 512 bytes of data are treated together as a sector, and reading and writing operations are performed in units of sectors. For designating storage locations in a hard disk, cylinder numbers, head numbers and cluster numbers of the hard disk are used. In order to unify reading and writing processes, storage areas of a hard disk are arranged, virtually, in a line. The storage areas of the hard disk are divided in plural sectors and the sectors are numbered. The numbers are called logic sector addresses. Logic sector addresses can also be defined in a similar manner in the case of a floppy disk.
When a hard disk in a host computer is accessed, logic sector addresses are used for designating data storage locations. Accordingly, it is convenient in terms of development of applications and data management if the same method for designating data storage locations can be used for memory cards such as ATA cards and SSFDC cards. For this reason, the memory cards need to be controlled in such a manner that data storage locations can be designated by using logic sector addresses.
When a memory card is connected to a digital camera, and the digital camera reads data from or writes data in the memory card, logic sector addresses are used to designate data storage locations. In other words, the digital camera operates as a host computer described above.
The memory card has a non-volatile memory apparatus, in particular, a flash EEPROM in its interior. The flash EEPROM has a memory area that is formed from a single block or is divided into a plurality of blocks, and each block is formed from a single page or is divided into a plurality of pages. Each page is structured to have the same unit storage capacity for reading and writing in a hard disk. For example, each page is provided with a memory area that is capable of storing 512 bytes of data. Also, as widely practiced, each page may be provided with an additional storage area of 16 bytes as a redundancy area. Although one page contains 512 bytes in the former structure, and one page contains 528 bytes in the latter structure, both of the structures are common to each other to the extent that they are capable of storing 512 bytes of data.
Storage locations within a flash EEPROM are readily determined by designating chip numbers of chips, block numbers of blocks in the chips, and page numbers of pages in the blocks. Storage areas within a flash EEPROM are arranged, virtually, in a line, and are successively numbered page by page from the head storage area. The numbers are called physical page addresses. In other words, storage locations within a flash EEPROM can be designated by the physical page addresses.
On the other hand, storage areas within a flash EEPROM are arranged, virtually, in a line, and successively numbered in units of blocks from the head storage area. The numbers are called physical block addresses. In other words, storage locations within a flash EEPROM can also be designated by the physical block addresses.
In the present application, designation of storage locations by the physical page addresses or by the physical block addresses is generally called as designation of storage locations by “physical locations”.
A flash EEPROM is an electrically erasable programmable read only memory. In other words, in principle, data can be written only once in an electrically erased page. Therefore, when data stored in any one of a plurality of pages is desired to be changed, the data in that page needs to be erased and then new data needs to be written. Further, flash EEPROMs are characterized in that the above-described erase operation is executed in units of blocks in order to reduce the number of devices and to increase the operation speed.
Other types of EEPROMs are equipped with a function of overwriting data in a page that already stores data. However, in most of the EEPROMs having the overwriting function of this type, the number of overwriting operations is limited. Also, there are a lot of other types of EEPROMs, which do not have the overwriting function.
The memory card converts a logic sector address designated by a host computer into a physical location, and performs writing and reading
Kimura Tsunenori
Kondo Yoshimasa
Gossage Glenn
Hogan & Hartson L.L.P.
Seiko Epson Corporation
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