Flash Memory has RAM

Hi,

Is there any Flash Memory that acts partly as RAM also ?

Thx in advans,
Karthik Balaguru

In article <76d3090a-f66e-465d-a28b-2beb32780f66
@s36g2000prg.googlegroups.com>, karthikbalaguru79@gmail.com says...
> Hi,
> 
> Is there any Flash Memory that acts partly as RAM also ?
> 
> Thx in advans,
> Karthik Balaguru
> 
Depends on what you mean here.  Many of the large NAND flash chips
have a 1K to 2KByte cache RAM on board.  However, their access
scheme makes them unsuitable for general data or program storage.

If you want data or program flash that can be read and written 
very often, like RAM,  you should look at the specs for some
of the FRAM (ferroelectric RAM)  chips.  They are non-volatile
like Flash, but can be read and written quickly like RAM.

Mark Borgerson

On 2007-11-22, karthikbalaguru <karthikbalaguru79@gmail.com> wrote:

> Is there any Flash Memory that acts partly as RAM also ?

FRAM acts sort of like a combination of Flash and RAM.  As does
core memeory.

-- 
Grant

Mark Borgerson wrote:

> If you want data or program flash that can be read and written 
> very often, like RAM,  you should look at the specs for some
> of the FRAM (ferroelectric RAM)  chips.  They are non-volatile
> like Flash, but can be read and written quickly like RAM.

There are also combinations of SRAM and EERPOM in one chip, which 
automatically save the SRAM contents to EEPROM on powerdown and restore 
on powerup. It takes only 10ms or so. Works very nicely. The only 
problem is the cost.

Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

On Nov 22, 10:02 pm, Mark Borgerson <mborger...@comcast.net> wrote:
> In article <76d3090a-f66e-465d-a28b-2beb32780f66
> @s36g2000prg.googlegroups.com>, karthikbalagur...@gmail.com says...> Hi,
>
> > Is there any Flash Memory that acts partly as RAM also ?
>
> > Thx in advans,
> > Karthik Balaguru
>
> Depends on what you mean here.  Many of the large NAND flash chips
> have a 1K to 2KByte cache RAM on board.  However, their access
> scheme makes them unsuitable for general data or program storage.
>

Interesting :):)
Thx to everyone for the info provided.

What is the difference between FRAM and NOR Flash Memory
w.r.t executing a complete application ?

I am thinking of a system where after reset/bootup
we need not copy the code from Flash to RAM and execute in RAM.
By this method, we will avoid the following
1) Time to copy from Flash to RAM
2) Acheiving Execution speed in Flash Memory just like RAM.

Thx in advans,
Karthik Balaguru

On Nov 23, 8:42 am, karthikbalaguru <karthikbalagur...@gmail.com>
wrote:
> On Nov 22, 10:02 pm, Mark Borgerson <mborger...@comcast.net> wrote:
>
> > In article <76d3090a-f66e-465d-a28b-2beb32780f66
> > @s36g2000prg.googlegroups.com>, karthikbalagur...@gmail.com says...> Hi,
>
> > > Is there any Flash Memory that acts partly as RAM also ?
>
> > > Thx in advans,
> > > Karthik Balaguru
>
> > Depends on what you mean here.  Many of the large NAND flash chips
> > have a 1K to 2KByte cache RAM on board.  However, their access
> > scheme makes them unsuitable for general data or program storage.
>
> Interesting :):)
> Thx to everyone for the info provided.
>
> What is the difference between FRAM and NOR Flash Memory
> w.r.t executing a complete application ?
>
> I am thinking of a system where after reset/bootup
> we need not copy the code from Flash to RAM and execute in RAM.
> By this method, we will avoid the following
> 1) Time to copy from Flash to RAM
> 2) Acheiving Execution speed in Flash Memory just like RAM.
>
> Thx in advans,
> Karthik Balaguru

You should be aware that processors with Instruction cacheing can run
significantly faster out of flash than the access time of the flash
would suggest - obviously this depends on application, cache size and
flash access time. But its worth bearing in mind if your code does
lots of tight looping. You can also sometimes lock code that you wish
to run fast (interrupt handlers being the obvious example) into cache.

Cheers
TW