Low Cost Wear Leveling for High-Density SPI NAND Flash in Memory Constrained Embedded System

SPI NOR Flash is widely used in embedded system for its compact package and simple interface. It is suitable to medium scale data storage. Now, industry provides higher density NAND Flash with the same interface and package as SPI NOR Flash. But the erase/program circles of NAND Flash is less than that of NOR Flash. The lifetime of NAND Flash is becoming the critical issue. Wear leveling algorithms prevent NAND Flash from prematurely retiring by mapping the logical block to different physical blocks. To our knowledge, most wear leveling algorithms need several kilobytes of RAM for keeping the mapping data structures, which is costly for the resource constrained micro controller. This study first proposes a no RAM required design with presetting lifetime, and then presents an adaptive design which requires only 2 kilobytes RAM with elasticity lifetime. The proposed design can be adapted in most of embedded systems based on low cost micro controller.