Storage device employing a flash memory
View Patent ↗A semiconductor disk wherein a flash memory into which data is rewritten in block unit is employed as a storage medium, the semiconductor disk including a data memory in which file data are stored, a substitutive memory which substitutes for blocks of errors in the data memory, an error memory in which error information of the data memory are stored, and a memory controller which reads data out of, writes data into and erases data from the data memory, the substitutive memory and the error memory. Since the write errors of the flash memory can be remedied, the service life of the semiconductor disk can be increased.
1. A storage device employing a flash memory,
wherein said flash memory is divided into a plurality of physical sectors identified by physical addresses,
wherein said flash memory carries out data write operation of write data from a host system into a sector of said plurality of physical sectors in response to a host logical address accompanied with said write data from said host system,
wherein said storage device includes a memory controller which generates a physical address in response to said host logical address for said data write operation of said write data from said host system,
wherein said memory controller carries out address conversion from host logical addresses to physical addresses to generates said physical address in response to said host logical address,
a method of operating the storage device, comprising:
assigning one physical sector selected, by said address conversion, from said plurality of physical sectors to a specific host logical address in a preceding data write operation in which preceding data from said host system is to be written into said one physical sector identified by a preceding physical address converted from said specific host logical address by said memory controller;
re-assigning another physical sector selected, by said address conversion, from said plurality of physical sectors to said same specific host logical address in a succeeding data write operation in which succeeding data from said host system is to be written into said other physical sector identified by a succeeding physical address converted from said same specific host logical address by said memory controller, said succeeding physical address being different from said preceding physical address, said succeeding data write operation being carried out in response to said same specific host logical address accompanied with said succeeding data from said host system after said preceding data write operation was carried out;
erasing old data of said one physical sector, identified by said preceding physical address, in which unnecessary data is written; and
storing a new correspondence between said succeeding physical address and said same specific host logical address within a table for said address conversion.
2. A method of operating the storage device according to claim 1 , wherein said memory controller carries out said preceding data write operation in which said preceding write data from said host system is written into said one physical sector selected from said plurality of physical sectors identified by said preceding physical address which is converted by said memory controller from said same specific host logical address,
wherein said memory controller carries out said succeeding data write operation in which said succeeding write data from said host system is written into said other physical sector selected from said plurality of physical sectors identified by said succeeding physical address which is converted by said memory controller from said same specific host logical address, and
wherein said succeeding data write operation is carried out within said storage device even though said one physical sector selected from said plurality of physical sectors is not defective and is usable before said succeeding data write operation.
3. A method of operating the storage device according to claim 1 , wherein even when data of a specific host logical address are frequently rewritten from said host system, the same physical address is not always used, but different physical addresses, which correspond to said same specific host logical address and are generated by said memory controller, are always used in data write operations of write data from said host system in response to said same specific host logical addresses accompanied with said write data from said host system.
4. A method of operating the storage device according to claim 2 , wherein even when data of a specific host logical address are frequently rewritten from said host system, the same physical address is not always used, but different physical addresses, which correspond to said same specific host logical address and are generated by said memory controller, are always used in data write operations of write data from said host system in response to said same specific host logical addresses accompanied with said write data from said host system.
5. A method of operating the storage device according to claim 1 , wherein said address conversion in said memory controller is carried out by address calculation using a pointer of said memory controller.
6. A method of operating the storage device according to claim 2 , wherein said address conversion in said memory controller is carried out by address calculation using a pointer of said memory controller.
7. A method of operating the storage device according to claim 3 ,
wherein said address conversion in said memory controller is carried out by address calculation using a pointer of said memory controller.
8. A method of operating the storage device according to claim 4 , wherein said address conversion in said memory controller is carried out by address calculation using a pointer of said memory controller.