SPRUIU1C July 2020 – February 2024 DRA821U , DRA821U-Q1
NAND flash architecture, introduced in 1989, is a flash technology. NAND is a page-oriented memory device; that is, read and write accesses are done by pages. NAND achieves great density by sharing common areas of the storage transistor, which creates strings of serially connected transistors (in NOR devices, each transistor stands alone). Because of its high density NAND is best suited to devices that require high capacity data storage, such as pictures, music, and data files. NAND nonvolatility makes of it a good storage solution for many applications where mobility, low power, and speed are key factors. Low pin count and simple interface are other advantages of NAND.
Table 12-4155 summarizes the NAND interface signals level applied to external device or memories.
Bus Operation | CLE | ALE | nCE | nWE (1) | nRE (1) | nWP |
---|---|---|---|---|---|---|
Read (cmd input) | H | L | L | RE | H | x |
Read (add input) | L | H | L | RE | H | x |
Write (cmd input) | H | L | L | RE | H | H |
Write (add input) | L | H | L | RE | H | H |
Data input | L | L | L | RE | H | H |
Data output | L | L | L | H | FE | x |
Busy (during read) | x | x | H (2) | H (2) | H (2) | x |
Busy (during program) | x | x | x | x | x | H |
Busy (during erase) | x | x | x | x | x | H |
Write protect | x | x | x | x | x | L |
Standby | x | x | H | x | x | H/L |