QUOTE
What is the differance between NOR and NAND Flash and when is one better over the other?
Hmmm, let me see.............
NAND-based solutions are ideal for high capacity data storage, while NOR is best used for code storage and execution, usually in small capacities.
Off the top of my head
NOR reads slightly faster than NAND
NAND writes MUCH faster than NOR
NAND erases much faster than NOR (2 msec vs. 4 sec)
Most writes must be preceded by an erase operation
NAND has smaller erase units for fewer erases in less time
NOR is memory mapped
NAND is I/O mapped
NOR is an XIP device
NAND is accessed in bursts of 512-2048 Bytes
NAND is available from 16MB to 512MB
NOR is available from 1MB to 32MB
NAND is better priced
NOR provides a good solution in low capacities from 1MB to 4MB
NAND has more than 10 times the life span of NOR
All flash suffers from bit-flipping issues
NAND suffers more from bit-flipping and requires EDC/ECC
NAND usually has some bad blocks randomly scattered throughout
NOR has a standard memory interface.
NAND is an I/O device and requires a relatively complicated driver
for any operation.
Using NAND requires bad block handling.
Using NAND requires implementing Error Detection/Correction
Code (EDC/ECC).
Reading from NOR requires no driver
Raw NAND has limited software support
CONCLUSION
Use of NOR devices is widespread, they offer an easy memory interface and are suitable for code execution, making them ideal for devices that do not need data storage. Their architecture makes them a good alternative in the range of 1MB to 4MB. NOR offers good read performance but poor write and erase times, disqualifying it from being used as a data storage
device. However, as todays devices become more and more sophisticated, they are expected to offer more features, richer programs and store more information locally. This requires larger capacities, both for code and data storage, and considerably faster erase/write times. NAND offers all of this, plus better prices in capacities ranging from 8MB to 512MB. However, most engineers are reluctant to use it due to its non-standard interface and complicated management.
thats about it.
This post has been edited by netdevil69: Feb 28 2005, 06:13 PM <
