Method and device to improve USB flash write performance
View Patent ↗A controller continuously or periodically interrogates the FAT table to determine which blocks are not storing data relative to any files stored in the memory at that time. If a block is located that is not allocated to a file, this block is erased and marked as being ready to receive data. In this way, a large file can be stored in the memory without having to wait for an erase operation to take place while the file is being written to the memory.
1. A flash memory subsystem including,
a flash memory which is divided into blocks, a fixed number of said blocks being maintained in erased status and ready to receive data, a File Allocation Table (FAT) being stored in said flash memory,
a memory controller operable to interrogate said FAT and to locate and erase memory blocks which have no sectors therein assigned to active files, said interrogating and erasing taking place during intervals when no files are being read or written to said memory,
whereby files larger that said fixed number of blocks can be written to said memory without waiting for an erase operation to take place.
2. The system recited in claim 1 wherein said memory is a NAND flash memory.
3. The system recited in claim 1 wherein said memory operates consistent with the SmartMedia specifications except for said interrogation and erase operations.
4. A memory system including,
a memory which requires an erase operation prior to a write operation, said memory being divided into blocks, a fixed number of said blocks being maintained in erased status and ready to receive data, a File Allocation Table (FAT) being stored in said memory,
a memory controller operable to interrogate said FAT and to locate and erase memory blocks which have no sectors therein assigned to active files, said interrogating and erasing taking place during intervals when no files are being read or written to said memory,
whereby files larger that said fixed number of blocks can be written to said memory without waiting for an erase operation to take place.
5. The system recited in claim 4 wherein said memory is a flash memory.
6. The system recited in claim 4 wherein said memory is a NAND flash memory.
7. The system recited in claim 4 wherein said memory operates consistent with the SmartMedia specifications except for said interrogation and erase operations.
8. The system recited in claim 6 wherein said memory operates consistent with the SmartMedia specifications except for said interrogation and erase operations.
9. The system recited in claim 4 wherein said memory has at least twenty four previously erased blocks, ready for a write operation.
10. A method of operating a memory which is divided into blocks and which requires that each particular block be erased prior to writing into each particular block, said memory having a file allocation table (FAT) stored therein, said method including the steps of:
interrogating said FAT when no read or write operations are taking place to identify blocks not assigned to current files,
erasing identified blocks when no read or write operation are taking place,
whereby large files can be stored in said memory without waiting for an erase operation to take place.
11. The method recited in claim 10 wherein said memory is a flash memory.
12. The method recited in claim 10 wherein said memory is a NAND flash memory.
13. The system recited in claim 10 wherein said memory operates consistent with the SmartMedia specifications except for said interrogation and erase operations.
14. A memory subsystem including:
a memory which is divided into blocks and which requires that each particular block be erased prior to writing into each particular block, said memory having a file allocation table (FAT) stored therein,
means for interrogating said FAT when no read or write operations are taking place to identify blocks not assigned to current files,
means for erasing identified blocks when no read or write operation are taking place,
whereby large files can be stored in said memory without waiting for an erase operation to take place.
15. The method recited in claim 14 wherein said memory is a flash memory.
16. The method recited in claim 14 wherein said memory is a NAND flash memory.
17. A system including a host computer in combination with the memory subsystem recited in claim 14 connected to said host by a Universal Serial Bus.
18. The memory system recited in claim 4 wherein said memory controller includes a Universal Serial Bus interface.
19. A system including a host computer in combination with the memory system recited in claim 18 , said host being connected to said memory system by a a Universal Serial Bus.
20. The flash memory subsystem recited in claim 1 wherein said memory controller includes a Universal Serial Bus interface.