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What exact eeprom on protoboard USB? — Parallax Forums

What exact eeprom on protoboard USB?

RaymanRayman Posts: 14,880
edited 2011-03-04 08:47 in Propeller 1
Anybody have a protoboard USB and a magnifying glass?

I'd like to know what kind of eeprom is on the protoboard USB...
I'm thinking about a board that needs at least a 400kHz I2C bus.
But, the documentation I see on the Parallax store website shows an obsolete part number.
I can't figure out if it's 100 or 400 kHz...

I'm not completely sure, but everything I've read so far suggests that running a 400kHz device on an I2C bus where 100kHz devices are present is a bad idea...

Comments

  • David BetzDavid Betz Posts: 14,516
    edited 2011-03-03 07:57
    It says "I3 A AT512" on mine.
  • RaymanRayman Posts: 14,880
    edited 2011-03-03 08:06
    David, Thanks. Do you see any symbols that might indicate the manufacturer?
  • David BetzDavid Betz Posts: 14,516
    edited 2011-03-03 08:10
    Rayman wrote: »
    David, Thanks. Do you see any symbols that might indicate the manufacturer?

    I can't see any symbols. Is it possible that the "I3 A" part (which was on a separate line) indicates the manufacturer?
  • RaymanRayman Posts: 14,880
    edited 2011-03-03 08:23
    David, thanks for looking... I think it might be Amtel, but I can't find a definitive match in a datasheet...

    Guess, I'll try asking Parallax...
  • max72max72 Posts: 1,155
    edited 2011-03-03 08:33
    Here is a close view.
    Hope it helps.

    Massimo
    eeprom.jpg
    640 x 480 - 82K
  • David BetzDavid Betz Posts: 14,516
    edited 2011-03-03 08:34
    Yup! That looks just like both of mine.
  • RaymanRayman Posts: 14,880
    edited 2011-03-03 15:48
    Well, Parallax answered my question and says it the same one as in their store:
    http://www.parallax.com/StoreSearchResults/tabid/768/List/0/SortField/4/ProductID/579/Default.aspx

    AT24C512

    Doesn't match the store photo...
    But, I guess I'll believe it since it's the answer I wanted to hear :)
  • TubularTubular Posts: 4,717
    edited 2011-03-03 16:06
    fwiw I've scoped the SCL line during prop bootup and it ticks over at about 300 kHz, so whatever they're using certainly isn't limited to 100 kHz.

    The reduced clock (<400kHz) is probably to allow for RC osc variation
  • RaymanRayman Posts: 14,880
    edited 2011-03-03 16:46
    Thanks Tubular!

    That's actually good solid info because that means every EEPROM used with the Prop must be good for 400kHz in order to work.

    I'd actually like to go to 1 MHz. I'm optomistic about this since this chip is rated for 1 MHz, although at 5V Vdd...
    Seems the the speed rating is somewhat dependent on Vdd, so at 3.3 V, maybe 700kHz is safe...
  • BigFootBigFoot Posts: 259
    edited 2011-03-04 08:47
    We are using The Amtel AT24C512B chip, they say it is good for 1 MHz under certain conditions.
    Our scope shows that the propeller reads the EEprom at 250 KHz with a 5 MHz crystal.
    pdf
    pdf
    At25c512.pdf
    675K
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