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FRAM instead of EEPROM? — Parallax Forums

FRAM instead of EEPROM?

abecedarianabecedarian Posts: 312
edited 2014-06-24 22:35 in Propeller 1
I think the title says it all.

Ignoring the cost, would it work on a P8X32A as an alternative to the EEPROM (instead of 24LC512 for instance)?
Would drivers need re-written?

http://www.cypress.com/?docID=48191

Comments

  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-06-22 20:58
    A long time ago and with the BasicStamp I was a FRAM enthusiast. But it seems the product has never quite found a real market niche. Maybe one day it will fit in, but there are so many alternatives.
  • jmgjmg Posts: 15,173
    edited 2014-06-22 21:36
    abecedarian wrote: »
    Ignoring the cost, would it work on a P8X32A as an alternative to the EEPROM (instead of 24LC512 for instance)?
    Would drivers need re-written?

    FRAM are designed to be serial compatible, so the i2c drivers would be unchanged, but the Device Address values likely do need changes.
    If you knew only FRAM was going to be used the code could even be simplified slightly, as there is no write delay/polling needed on FRAM. (and no power-failing handler either )

    Of course FRAM parts are quite costly, so you really have to need some of their features.
  • abecedarianabecedarian Posts: 312
    edited 2014-06-22 21:46
    Loopy Byteloose wrote: »
    A long time ago and with the BasicStamp I was a FRAM enthusiast. But it seems the product has never quite found a real market niche. Maybe one day it will fit in, but there are so many alternatives.
    Well, not sure about not finding a niche, but it's finally hitting the hobbyist space; not going to post about it here. But still not too cheap unless it's embedded in an MCU.
    jmg wrote: »
    FRAM are designed to be serial compatible, so the i2c drivers would be unchanged, but the Device Address values likely do need changes.
    If you knew only FRAM was going to be used the code could even be simplified slightly, as there is no write delay/polling needed on FRAM. (and no power-failing handler either )

    Of course FRAM parts are quite costly, so you really have to need some of their features.
    Yeah, the part I linked to was almost $14 USD.

    I was thinking more about faster boot time and write endurance than anything though; thinking about something for the EFI / ECU project I've been batting my head against. Just exploring options. ;)
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-06-23 04:42
    It is really hard to justify the cost if you have never worn out an EEPROM. I don't think it would be hard to interface to the Propeller. And it just may be a drop in replacement for the boot EEPROM.

    But you look at $9 for a Propeller chip and $14 for a FRAM, you begin to wonder. Paying $6 for an ADC chip is another awkward reality (MCP3208 from Parallax), but that seems worthwhile.

    They would work with BasicStamps, too.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2014-06-23 07:43
    As jmg mentioned the addresses aren't the same. The Prop wouldn't be able to boot from FRAM. At least this is the impression I received from reading previous threads on the topic.

    I don't know if they still give samples, but a while back (two years?) the company making FRAM (Ramtron?) would give you three samples for the asking.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-06-23 08:08
    Yeah, I see now.
    Addressing compatibility is really a cluster of issues.

    A. The I2C bus
    B. The actual packages pins to produce 3 bits of a package address
    C. Most significant bit first or Most significant bit last
    D. The scheme that uses 8 bit control and/or 16 bit address with additional features for writes and read of contiguous blocks of bytes.

    A, B, and C appear to be the same. D would take a comparitive reading of both products PDFs to determine how unalike they are.
  • BasherBasher Posts: 25
    edited 2014-06-23 08:55
    I've used this http://uk.rs-online.com/web/p/fram-memory-chips/7165763/ with the propeller. I got it for the RTC but it also has 32K of fram memory on a I2C bus that worked fine as the props boot eeprom. There was no real advantage to using it though. The fram is faster than the normal eeprom but when the propeller is using it to boot from it doesn't take advantage of the faster speed.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2014-06-23 10:04
    Basher wrote: »
    worked fine as the props boot eeprom.

    Cool. Good to know.
  • jmgjmg Posts: 15,173
    edited 2014-06-23 14:56
    abecedarian wrote: »
    I was thinking more about faster boot time and write endurance than anything though; thinking about something for the EFI / ECU project I've been batting my head against. Just exploring options. ;)

    See #8 - Boot times is locked in the Prop ROM.
    Write endurance and write speeds are the main 'gains' with FRAM.

    Write Speed in EEPROM is hard to work around, if you really need fast writes, FRAM can self-select.

    Endurance, you can engineer a little, and most EE devices have ECC
    See for example
    ftp://ftp.microchip.com/tools/memory/total50/tutorial.html

    and this
    http://www.st.com/web/en/resource/technical/document/datasheet/CD00001891.pdf
    mentions 4 Million WR cycles @ 25 °C, < 5ms Twr
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-06-24 01:04
    Basher wrote: »
    I've used this http://uk.rs-online.com/web/p/fram-memory-chips/7165763/ with the propeller. I got it for the RTC but it also has 32K of fram memory on a I2C bus that worked fine as the props boot eeprom. There was no real advantage to using it though. The fram is faster than the normal eeprom but when the propeller is using it to boot from it doesn't take advantage of the faster speed.

    That is the one I fell in love with. The addition of a Real Time Clock is a big boost in utility. The fact that the Propeller will boot from it makes it good to.
  • abecedarianabecedarian Posts: 312
    edited 2014-06-24 22:35
    All great advise and information!
    Thanks. :)
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