Wear leveling techniques for flash EEPROM systems
US6230233A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 13, 1991 |
| Grant date | May 8, 2001 |
| Priority date | — |
| Expiry date | Sep 13, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F2212/7211
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A mass storage system made of flash electrically erasable and programmable read only memory ("EEPROM") cells organized into blocks, the blocks in turn being grouped into memory banks, is managed to even out the numbers of erase and rewrite cycles experienced by the memory banks in order to extend the service lifetime of the memory system. Since this type of memory cell becomes unusable after a finite number of erase and rewrite cycles, although in the tens of thousands of cycles, uneven use of the memory banks is avoided so that the entire memory does not become inoperative because one of its banks has reached its end of life while others of the banks are little used. Relative use of the memory banks is monitored and, in response to detection of uneven use, have their physical addresses periodically swapped for each other in order to even out their use over the lifetime of the memory.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.