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Serial Memory ..

Justin PentecostJustin Pentecost Posts: 14
edited 2005-01-13 19:10 in BASIC Stamp
I have a job that needs a large ammount of data (possibly as much as 64KB) to be held locally for access by the stamp.··· In theory an EEPROM would be fine, however I was wondering if there was on the the market a serial volatile RAM chip using the same protocol as the ST series EEPROM's ?

Does anyone know of such a chip ?

Justin

Comments

  • Donald BartleyDonald Bartley Posts: 19
    edited 2005-01-09 20:55
    I use the Phillips Semiconductor I2C SRAM PCF8570PN in alot of my projects.· I'm affaird it will fall short of your memory requirements as it is only 256 bytes but it does work great as a SRAM memory expander for the Stamp.· You can get them from Arrow Electronics.

    Don
    ·
  • allanlane5allanlane5 Posts: 3,815
    edited 2005-01-10 00:41
    The solutions-Cubed RAM module might do what you are wanting. I suspect they max out at 32 K Bytes though. It's interfaced with SERIN/SEROUT at 9600 baud.
  • Justin PentecostJustin Pentecost Posts: 14
    edited 2005-01-11 20:22
    allanlane5 said...
    The solutions-Cubed RAM module might do what you are wanting. I suspect they max out at 32 K Bytes though. It's interfaced with SERIN/SEROUT at 9600 baud.
    Thankyou very much This looks like it's what I want [noparse]:)[/noparse]

    Justin
    ·
  • achilles03achilles03 Posts: 247
    edited 2005-01-11 20:44
    Here's a really good solution also: AT25HP512. It's an 8-pin eeprom with SPI interface, just like the one Parallax offers on the IC page, only it's got 64K of memory instead of 8k. It's just under $8 too. I like the SPI interface a little better, as it's easier to work with than I2C (my opinion though). If you want, there's some with 32k that run a little cheaper...

    Just make sure you order one that will operate at 5V, as some are designed for lower voltages (like 3). You probably also want to make sure it's DIP, and not SOIC.

    Here's the datasheet for one you might want:
    http://rocky.digikey.com/WebLib/Atmel/Web Data/AT25HP256,512 (2001).pdf

    Hope that helps,
    Dave
  • NewzedNewzed Posts: 2,503
    edited 2005-01-11 20:51
    Dave, if I may offer a bit - the AT25F512 is a much better chip.· It is byte addressable, whereas the AT25HP is page write only.· Unfortunately, the chip is now obsolete, but you might be able to find them somewhere.· I have four or five - they are the chip for my piggyback EEPROM.· I was really sorry to see that chip die out - makes a fantastic EEPROM, running at 3.3 volts.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Sid Weaver
    Do you have a Stamp Tester?

    http://hometown.aol.com/newzed/index.html
    ·
  • achilles03achilles03 Posts: 247
    edited 2005-01-11 21:00
    Wow, you're right... my bad. I didn't see the "page write only" statement. I was about to order some too.

    Ok Justin, check this one out:

    AT25256
    http://rocky.digikey.com/WebLib/Atmel/Web Data/AT25128,AT25256.pdf

    SPI, byte addressable, operates at 5V, 32k.

    There might be other 64k or even higher eeproms out there, but those are just some that I pulled off digikey. Mouser or others might have more.

    Dave
  • NewzedNewzed Posts: 2,503
    edited 2005-01-11 21:13
    Dave, I have searched everywhere I can think of, but I can not find a byte addressable EEPROM - everything is page write.· What a pity - if you only want to store 8 bytes at a time, it takes a whole page, which is usually 256 bytes.

    The Ramtron FM31256 might be byte addressable - I'm not sure.· I have three or four samples chips which I have never used.· They are quite expensive so I didn't consider them for my piggyback.· The do have unlimited read/write since the are ferro-electric and they also have a built-in RTC.· Quite a complicated little chip.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Sid Weaver
    Do you have a Stamp Tester?

    http://hometown.aol.com/newzed/index.html
    ·
  • achilles03achilles03 Posts: 247
    edited 2005-01-11 21:31
    You mean you haven't found anybyte addressable eeproms that are 64k, right? I have a bunch of 8k's at home, not to mention the ones Parallax sells. That 32k I listed above looks like it'd be good too (both byte and page writeable). The eeproms I've used can write a single byte, or a whole page. Once you've entered the write command, you just shiftin 1, 2, 3, etc... bytes of data until you're done (or you hit the page write limit).

    Dave
  • Robert KubichekRobert Kubichek Posts: 343
    edited 2005-01-11 21:39
    Why don't you try the uMMC serial data module??? It uses Sd/Mmc memory packs.

    www.roguerobotics.com
  • Jim McCorisonJim McCorison Posts: 359
    edited 2005-01-11 22:49
    For multi-megabyte storage needs the uMMC looks pretty handy. But, $100 + $20 for a 64mB card (the smallest I found on a quick search), to store 64kB is a bit pricey.

    Jim

    Just noticed that it's $95 _Canadian_, plus shipping of course. But it's still spendy for storing only 64kB.
  • achilles03achilles03 Posts: 247
    edited 2005-01-11 22:57
    You mean 64MB...

    However, I can't even conceive of a datalogging project using a BS2 that would need that much memory.
  • Jim McCorisonJim McCorison Posts: 359
    edited 2005-01-11 23:30
    No I meant 64kB. Justin's requirement is for 64kB.

    My point is that while the uMMC may be a nice piece of kit, and the storage capacities are certainly up there, the minimum card size seems to be 64mB and that the total price to store only the required 64kB puts it well beyond EEPROM or NV SRAM prices.

    Jim

    Post Edited (Jim McCorison) : 1/12/2005 4:50:32 PM GMT
  • achilles03achilles03 Posts: 247
    edited 2005-01-13 19:10
    For future reference, here's a bunch of 32kB SPI eeproms (available in 8-DIP package), 5V, with single-byte and page write capabilities:

    AT25256 - Amtel
    (CAT)25C256 - Catalyst
    M95256-BN6 - STMicroelectronics

    All can be found on digikey and/or mouser. The Catalyst and STM versions are about $2.85 and $2.70 respectively.

    Dave
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