Meet Different Needs with NANDand NOR

摘要

For the last few years the media has debated which Flash memory technology, NAND or NOR, will emerge as the market winner. This discussion implies that the different Flash technologies are essentially interchangeable in applications, making the two direct competitors for design wins. The reality is, the two technologies address different needs. Understanding the differences between the technologies begins with their names. The original approach to Flash memory followed the structure of other semiconductor memories, which achieve random access by connecting the memory transistors to the bit lines in parallel. Each transistor has a word line and a bit line connection. In this arrangement, if the word line turns on any memory transistor, the transistor connects drain to source and the corresponding bit line goes low. The logic function is similar to that of a "wired NOR", hence the name NOR for this arrangement.