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'[EE:] Ramtron FRAM - susceptability?'
2004\07\21@192704 by Brent Brown

picon face
Hi,

Interested to hear from anyone experienced with Ramtron Ferroelectric
Nonvolatile RAM chips. I have a micro board that is experiencing occasional
corruption of data stored in a FM24C256 FRAM chip. I wondering if these
things are sensitive to electric/magnetic fields?

I can not rule out errant code on the micro causing the corruption by errant
writes to the FRAM, but also the level of EMI in this application is not
insignificant which makes me curious. We have had problems with radiated
EMI from this board design in the past, and that was overcome by metal
coating the inside of the plastic enclosure.

Any comments welcome. I'm curious enough to start some doing some
bench tests to see if I can corrupt the contents of the FRAM.

--
Brent Brown, Electronic Design Solutions
16 English Street, Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/txt: 025 334 069
eMail:  spam_OUTbrent.brownTakeThisOuTspamclear.net.nz

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2004\07\21@201408 by Bob Axtell

face picon face
Good Q.

Brent Brown wrote:
> Hi,
>
> Interested to hear from anyone experienced with Ramtron Ferroelectric
> Nonvolatile RAM chips. I have a micro board that is experiencing occasional
> corruption of data stored in a FM24C256 FRAM chip. I wondering if these
> things are sensitive to electric/magnetic fields?
>
I've designed them into lotsa stuff over the years, without the
slightest failure.

> I can not rule out errant code on the micro causing the corruption by errant
> writes to the FRAM, but also the level of EMI in this application is not
> insignificant which makes me curious. We have had problems with radiated
> EMI from this board design in the past, and that was overcome by metal
> coating the inside of the plastic enclosure.
>
Thats possible, of course.

> Any comments welcome. I'm curious enough to start some doing some
> bench tests to see if I can corrupt the contents of the FRAM.

What I DO know is that it is NOT affected by a powerful alnico magnet.
I've never understood exactly what is going on, but they certainly work.

Let us know what you find out!
{Quote hidden}

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        Bob Axtell
PIC Hardware & Firmware Dev
  http://beam.to/baxtell
      1-520-219-2363

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2004\07\22@045002 by Philip Pemberton

face picon face
In message <40FF06CF.3030103spamKILLspamcotse.net>
         Bob Axtell <.....engineerKILLspamspam.....COTSE.NET> wrote:

> I've designed them into lotsa stuff over the years, without the
> slightest failure.
I've used FRAMs too - never had a failure. Well, except for the time I fudged
the write timing and ended up having the chip write randomness to its memory
array, but that was entirely my fault :)

> What I DO know is that it is NOT affected by a powerful alnico magnet.
I've tried with a neodymium magnet from a hard disk actuator assembly. A good
five minutes of waving the magnet in various directions - nothing. Well,
except for the weird colour patterns on a nearby monitor. Oops.

> I've never understood exactly what is going on, but they certainly work.
Same here. The only differences between an FRAM and an E2PROM that really
matter are the write timing (no 10mS write delay - yay!) and the fact that
reads are destructive. Basically, the chip's onboard controller circuitry
reads the contents of a given memory cell, then writes it back and sends the
data it read back to the host device.

They're nice chips - I think Ramtron are on to a winner here. I'm waiting
until they start producing 256 and 512kbit FRAMs - they'd be perfect for
sound recording and replay :)

Later.
--
Phil.                              | Acorn Risc PC600 Mk3, SA202, 64MB, 6GB,
EraseMEphilpemspam_OUTspamTakeThisOuTdsl.pipex.com              | ViewFinder, 10BaseT Ethernet, 2-slice,
http://www.philpem.dsl.pipex.com/  | 48xCD, ARCINv6c IDE, SCSI
... 24 hours in a day, 24 beers in a case, Hmmm.....

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'[EE:] Ramtron FRAM - susceptability?'
2004\08\04@002033 by Brent Brown
picon face
Belated reply...thanks to all who posted comments/ideas to my original
query. That was only 2 weeks ago.

Project is slipping into never-never land for a while due to lack of funding on
my clients part. Shame. Hopefully though it will come back again and I'll be
able to post the answer back here. They have found enough finances for the
firmware to be overhauled (again, not by me), so there's a chance the
problem may disappear when that is done.

Best regards, Brent.

--
Brent Brown, Electronic Design Solutions
16 English Street, Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/txt: 025 334 069
eMail:  brent.brownspamspam_OUTclear.net.nz

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