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EEPROM lifetime — Parallax Forums

EEPROM lifetime

Smoke Liberation FrontSmoke Liberation Front Posts: 30
edited 2005-12-04 18:31 in BASIC Stamp
It's me again...

I remember seeing that the EEPROM can only be written to a fixed number of times.

What is that number for a BS2p40? What happens when I write one time too many?

Does the BS know that the memeory has been written to too many time and flagg and error? Or will I get garbage?

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Freeing smoke from wire and IC captivity since 1972

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-12-02 19:43
    The Stamp does not keep track of how many times you've written to a cell -- where would it store this information? (That will make sense if you think about it for a minute). If you do make an EEPROM go bad, you'll get a "EEPROM failure" complaint from the compiler. If you're doing general purpose programming you should never see this. If you're doing high-speed datalogging, you might consider using an external EEPROM (we've got lots of demo code).

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    Jon Williams
    Applications Engineer, Parallax
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-12-02 19:48
    I tried reading the part number off the picture they have, but I couldn't make it out. The low end for reprogramability is 10k, with some being 100k writes. So that would be the number of times you program it. Even if you reprogram it once a day, thats still 27 years before you'll run into problems, so I wouldn't be too concerned about it. However if you are using the EEPROM to rapidly store and subsequently change data in you programs, you could see it wear out rather quickly.

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-12-02 20:37
    The following web page has the write lifetime for each BASIC Stamp Model.

    http://www.parallax.com/html_pages/tech/faqs/prgm_info.asp#How_does_my_program_get_stored_in_the_Stamp

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • T&E EngineerT&E Engineer Posts: 1,396
    edited 2005-12-02 21:03
    I did not see the BS2px listed so I am still assuming it falls under the BS2p catagory of 100,000 cycles.
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-12-02 21:19
    The BS2px uses the Microchip 24FC128-I (industrial) EEPROM which is rated for 1,000,000 erase/write cycles.

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    Jon Williams
    Applications Engineer, Parallax
  • Smoke Liberation FrontSmoke Liberation Front Posts: 30
    edited 2005-12-03 19:31
    I don't know why I thought EEPROM was only for data... Thanks for letting know that though the memory has a finite life, I'll likely be retired before I wear it out!


    This is great info! Thanks everyone.

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    Freeing smoke from wire and IC captivity since 1972
  • allanlane5allanlane5 Posts: 3,815
    edited 2005-12-04 18:31
    Yup, a million writes is a lot -- unless your program runs crazy and writes to the same location every millisecond. Then you can 'use it up' in about a week.

    And a "used up" location won't program. Thus, when erased to a zero, then when the IDE tries to program it to any other value than zero, it doesn't succeed. That's why the 'verify' step fails at that point.

    However, if you don't actually USE the location, then the IDE won't detect it is bad. In the code area this doesn't help, but in the data area you might be able to adjust the eeprom areas you use (if any).
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