Embedded Systems Course- module 16: Flash memory basics and its interface to a processor

Introduction: Flash memory or a flash RAM is a type of nonvolatile semiconductor memory device where stored data exists even when memory device is not electrically powered. It's an improved version of electrically erasable programmable read-only memory (EEPROM). The difference between Flash Memory and EEPROM are, EEPROM erases and rewrite its content one byte at a time or in other words, at byte level. Where as Flash memory erases or writes its data in entire blocks, which makes it a very fast memory compared to EEPROM. Flash memory can't replace DRAM and SRAM because the speed at which the DRAM/SRAM can access data and also their ability to address at byte level can't be matched by Flash. The flash memory is also termed as Solid-state Storage Device (SSD) due to the absence of moving parts in comparison to traditional computer hard disk drive. Flash memory types: The two main types of flash memory are the NOR Flash & NAND Flash. Intel is the first company to introduce commercial (NOR type) flash chip in 1988 and Toshiba released world's first NAND-flash in 1989. NOR-flash is slower in erase-operation and write-operation compared to NAND-flash. That means the NAND-flash has faster erase and write times. More over NAND has smaller erase units. So fewer erases are needed. NOR-flash can read data slightly faster than NAND. NOR offers complete address and da...