I have a question about NAND flash interface.

Hi guys.
I am looking for the information about the flash memory.
but i read a article from the below link.
  http://www.bellevuelinux.org/flash_memory.html
It said , NOR can do random-acess on read and write. NAND, however,
its input/output interface allows only sequential access to data.

is that true?
so with NAND flash how can you find out your data?
just do sequestial searching??? too stupid i think..

please give me the right answer.
anyway thanks for reading
Have a nice day

>From Namh.

gaedduck@gmail.com wrote:

>Hi guys.
>I am looking for the information about the flash memory.
>but i read a article from the below link.
>  http://www.bellevuelinux.org/flash_memory.html

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

http://en.wikipedia.org/wiki/Flash_memory
http://www.linuxdevices.com/articles/AT4422361427.html
http://www.linuxdevices.com/articles/AT6503806063.html
http://www.embedded.com/showArticle.jhtml?articleID=165701775
http://download.micron.com/pdf/technotes/nand/tn2916.pdf

>so with NAND flash how can you find out your data?
>just do sequestial searching??? too stupid i think..

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.

-- 
Guy Macon
<http://www.guymacon.com/> 

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

On Aug 12, 11:14 am, gaedd...@gmail.com wrote:
> Hi guys.
> I am looking for the information about the flash memory.
> but i read a article from the below link.
>  http://www.bellevuelinux.org/flash_memory.html
> It said , NOR can do random-acess on read and write. NAND, however,
> its input/output interface allows only sequential access to data.
>
> is that true?
> so with NAND flash how can you find out your data?
> just do sequestial searching??? too stupid i think..

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.

gaedd...@gmail.com wrote:
> Hi guys.
> I am looking for the information about the flash memory.
> but i read a article from the below link.
>   http://www.bellevuelinux.org/flash_memory.html
> It said , NOR can do random-acess on read and write. NAND, however,
> its input/output interface allows only sequential access to data.
>
> is that true?
> so with NAND flash how can you find out your data?
> just do sequestial searching??? too stupid i think..
>
> please give me the right answer.
> anyway thanks for reading
> Have a nice day
>
> >From Namh.

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!