I have a question about NAND flash interface.

I don't like the way that page describes things. It isn't very clear and misses important details. or a far better explanation, see

Are hard disks stupid?

Random-access NOR is more expensive, less dense, and can read (not write) randomly located data very quickly. It is a good choice for executable code in embedded devices.

Sequential-access NAND has a lower cost, higher density, and has a better balance between reading, writing and erasingtimes, and often has a longer life expectancy under many read-write cycles. It is a good choice for data storage when the data is organized into files.

Another choice is Pseudo-NOR PNOR, which iss really NAND with a RAM cache. This reduces read-write cycles and allows random access.

Or you can use an SST (Silicon Storage Technology) All-in-OneMemory device. The new SST88VP1107 has 512K of instant-on boot NOR, 128M of PNOR (4M RAM cache) that can execute in place, 120 MByte NAND for data storage 12M of RAM, all on one device. It also has a memory- mapped ATA interface, a built-in Flash File System, Memory Management Unit and hardware Error Checking and Correcting (correct 8 random bit errors). They are estimating $17.00 each, Qty=10K and are now sampling. Note: I have *not* usede this part myself. The above info comes from the manufacturer's literature, not my experience.

Thanks for your answer and links.:) But one more question is coming out.;)

You said NAND has sequential-access like HDD. but what's the difference between HDD sequential-access and Tape sequential-acess. I think the Tape is typical example for sequential-access. but i don't think HDD is.

plz, save the foolish guy like me. :) have fun. thanks for reading

Namhun

Yes NAND is harder to access a given piece of data, that is why they also provide NOR flash with true random access. But NAND is not fully sequential. You address pages (or whatever term is used for the smallest block of addressable data). The data of that page is read out sequentially until you get all of the data you wanted. It is difficult to try to execute code directly from the flash, but if you are just copying the code or data to RAM, you can do it in pages which are typically 2 kB or smaller. Many systems work that way with larger DRAMs for direct, random access and NAND flash for non-volatile storage. It's a nice combination and works much faster than NOR flash alone.

What NAND will you use? Just take a few hours to read the data sheet. It is very easy to understand if you have HW background!