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PICList Thread
'PIC RAM: SMT Serial RAM? PIN match to Atmel AT45D0'
1999\08\06@140920 by eplus1

Is there a RAM equivalent of the Atmel AT45D081? Or just a good serial RAM
on one chip (not someone's parallel ram with a PIC to convert to serial). I
have a proto board almost done and would like to add space for external RAM
to complement the up to 4 megs of 2 wire (SO and SI combined, CS is SCK
through one-shot) SPI FLASH but (get ready for something you have never
heard before) I'm low on IO pins and board space. Any ideas very much

James Newton, webmaster <>
1-619-652-0593 phoneÊ

1999\08\09@152448 by eplus1

By way of answering my own question (sort of) the Serial FRAM from
RAMTRON     is a non-volatile high speed (IIC at 200k or SPI at 2.1MHz w/ no
write delay) memory with unlimited write endurance. As of today only
available in 2k bytes or less but larger sizes are planned. Rep by distributed by approx.
$2.95 each for the 2kB part and they say that have many thousands in-stock
(offered sample etc...). Its not AT45d081 pin compatible but since its only
a 8 pin DIP or SMT, finding room next to all the wasted space in 28 or 32
pin space required for the Atmel serial FLASH shouldn't be hard.

RAMTRONs FRAM is based on a fairly new (1996) technology and very few
mentions on the search engines (CUBIC Corp, SGS-Thomson, Samsung signed on
in 1997) but their stock has been steady dropping for a while and only one
engineer I found has any application stories (CCS PCM Routines to use the
FM24C16 so I would
love to know why people are not using them. Some items of interest are
listed here:
- Previous mention on the PICLIST indicates that availability / lead time
have been a problem.
- PICLIST Post on possible problem with invalid writes on processor fail
- NASA Radiation tests
- Background article from Forbes online
- Background article from Byte online

Mention was made in a PICLIST post
( of a "DS1280, which
interfaces a 3-wire micro-wire bus to up to 512K of SRAM" which I do not
find on the mfgrs site.

I'm still amazed that no one else is making a standard SRAM in multi-KB
sizes with a SPI or I2C interface. A pin replacement for an Atmel Dataflash
(when it turns out that life time is a problem and power is not) would be a
good seller...

No all I have to do is answer my own "IEEE 1284 PP data direction changes
[OT?]" question that everybody carefully ignored... <GRUMBLE> <SIGH> I hate
it when I have to do my own work <GRIN>

James Newton, webmaster <>
1-619-652-0593 phoneÊ

{Original Message removed}

1999\08\10@145049 by Mark Willis

I seem to remember something about some kind of a limited lifetime on
these (Maybe it's not limited writes, but limited READs?)  Maybe that's
from their web pages.


James Newton wrote:
{Quote hidden}

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