Is NAND Flash an asynchronous memory?

[jamesnguyen]

Hi everyone,

Is NAND Flash an asynchronous or synchronous memory? How can I tell?

From what I understand, synchronous memory requires a clock signal, but there isn't seem to be one on a NAND Flash... I could be wrong, though.

No, this is not a homework question.
Regards,
James

 

[IRstuff]

If it weren't synchronous, how would you possibly use it? HAve you even looked at its datasheet?

TTFN

FAQ731-376

 

[jamesnguyen]

You don't have to be harsh. If you don't want to help, just don't answer.

From the Blackfin's external memory bus description:

"The external bus interface unit (EBIU) provides glueless interfaces to external memories. The processor supports Synchronous DRAM (SDRAM) including mobile SDRAM. The EBIU also supports asynchronous interfaces such as SRAM, ROM, FIFOs, flash memory, and ASIC/FPGA designs"

Does it sound to you like the flash memory is asynchronous?

"If it weren't synchronous, how would you possibly use it?" Well, I am here to learn. Maybe you should too!

Regards,
James

 

[IRstuff]

And why would I have refered to the datasheet for a processor you never mentioned, as opposed to the datasheet for any NAND flash memory?

Which, would have something like:
READ ENABLE
The RE input is the serial data-out control, and when active drives the data onto the I/O bus. Data is valid
tREA after the falling edge of RE which also increments the internal column address counter by one.

TTFN

FAQ731-376

 

[MacGyverS2000]

The EBIU also supports asynchronous interfaces such as SRAM, ROM, FIFOs, flash memory, and ASIC/FPGA designs"

Does it sound to you like the flash memory is asynchronous?

I'm not sure it gets any more clear than that...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[geekEE]

There actually are a few synchronous flash parts. However, the vast majority are asynchronous. Look at the data sheet for any specific flash part to tell which it is.

Glenn

 

[MacGyverS2000]

geek,

Any examples of those synchronous parts? Synchronous clocking of (comparatively) slow components seems like a tough row to hoe...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[geekEE]

Ok. I just reread the post and realized that the OP is asking about NAND flash. My answer was more appropriate to NOR flash. In NOR flash, synchronous operation was used by the now obsolete Intel 28F016XS and a few other parts.

In NAND flash, many parts can operate in either synchronous or asynchronous mode. Check out the ONFI specification. And there is a CLK line when operating in synchronous mode.

Glenn

 

[benta]

NAND Flash usually do not connect to the EBI.
They need a controller, much like a harddisk interface, as read/write operations are on whole sectors, not bytewise.

Benta.

 

[jamesnguyen]

Thank you everyone for your reply. It really helps.

Best regards,
James