a. What are the difference between Nor and NAND flash (architecture , advantage....)?
NOR flash
- core cells connected in parallel (common ground)
- adv. random access (good for code execution)
- adv. faster than NAND flash
- disadv. larger area than NAND flash with the same capacity
NAND flash
- core cells connected in series (normal 8 or 16 cells)
- adv. smaller than NOR flash with the same capacity (cos connected in series)
- disadv. slower than NOR flash (cos stack transistors)
- disadv. sequential access (good for data storage but not code execution)
b. Market share rank in NOR flash:
1st Spansion
2nd Intel
3rd STM
1) NAND flash have much more capacity, but slower and can have 'bad sectors', needs bad sector management (Multimedia, Smartmedia cards);
2) NOR flash faster, have parallel address/data buses, used mostly as 'BIOS' in microcontroller systems.
NOR FLASH - is like ROM memories
1.less storage capacity comapre to NAND
2.fast read
3.slow erase and write
4.requires external error detection
5.easy interfacing cktry
NAND Flash: - is like mass storage devices like hard disk
1,Huge storage capacity
2.slow in random access
3.fast erase and write
4.internal error detection provision
5.complex interface circuitry