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Thread: Xircom Pocket Ethernet EEPROM unreadable error

  1. #11

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    I took apart the adapter to have a look inside. It is very easy to take apart - just slide the red rubber grip loop off the one side and then pry it open with a credit card. There are no screws, it just pops open.

    A photo of the board is below. I had to crush the quality somewhat to be able to attach to the post but it is still readable. It is the PE3-10BC model which has both BNC and RJ45 connectors

    pe3-circuitboard-reduced.jpg

    Some of the notable chips on the board:
    ST C06CM1 - EEPROM chip (datasheet) is just to the left of the main Xircom chip

    PE-65745 - Lan isolation transformer (datasheet)

    Xircom 2001773A / MB87328 - Xircom custom chip

    Fil-Mag 91 SM - ???

  2. #12

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    Quote Originally Posted by jhhoward View Post

    Fil-Mag 91 SM - ???
    DC-DC converter, 12V in - 9V out, isolated (as far as I remember, I haven't worked with old school boards in 20 years or so).

    Frank IZ8DWF
    Last edited by iz8dwf; August 12th, 2020 at 05:37 AM.

  3. #13

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    Quote Originally Posted by iz8dwf View Post
    DC-DC converter, 12V out, isolated (as far as I remember, I haven't worked with old school boards in 20 years or so).
    I know you can power these using a PS/2 passthrough cable so perhaps this is for ensuring a clean 12V?

    Looking at the EEPROM chip docs it is possible to write new data to the chip easily enough (assuming it isn't damaged). I'm sure there must be a way to actually do this by just writing a DOS program without any hardware modifications needed. The only problem is the Xircom interface is completely undocumented so there is no way to know how.

    The EEPROM chip itself is really small so would be very tricky to remove from the board. Would it be possible to solder wires directly to the pins (whilst the chip is still on the board) and hook up to an Arduino to reprogram?

    Alternatively if I could read the voltage of the pins it might help if trying to reverse engineer the Xircom protocol for accessing the EEPROM.

    Any other ideas?

  4. #14

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    The coupling transformers and the DC/DC are part of the requirement for ethernet cables to be completely floating respect the host's electronic power rails. If you notice, also the BNC connectors were insulated with a plastic ring from the mounting hole/tab.
    As for the EEPROM, you can either remove it and try to reprogram or substitute it, or you can try to reverse engineer the protocol. If you hook wires to the circuit, you end powering the whole board unless you at least disconnect the power pin on the EEPROM chip.
    Programming the chip with the rest of the circuit also powered might or might not work, and you could also introduce new problems.

    Frank

  5. #15

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    http://bitsavers.trailing-edge.com/c..._Data_Book.pdf
    MBL8392A - Coaxial Transceiver Interface for EthernetlThin Ethernet... ........................... 247

    physical page 250-259

  6. #16

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    HYUNDAI HY62255A Series 32K X 8-bit CMOS SRAM
    https://datasheet.datasheetarchive.c...2IH0067050.pdf

    poor quality

  7. #17

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    Has anyone dumped a working EEPROM's contents? I'd like to be able to alter the MAC address and flash new chips. It looks like there's many modern EEPROMs that are package and signal compatible and can be programmed with SPI.

  8. #18
    Join Date
    Mar 2013
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    SW Quadrant of Michigan
    Posts
    279

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    Sorry for not getting this done yet. I've been neck deep with a broken water main and 6" of standing water. I promise I will get to it soon.

  9. #19

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    Quote Originally Posted by Paralel View Post
    Sorry for not getting this done yet. I've been neck deep with a broken water main and 6" of standing water. I promise I will get to it soon.
    That sounds awful, sorry to hear it. Best of luck to you!

    I also need to test programming these EEPROMs. These EEPROMs are Microwire which is a subset of SPI. I bought a cheap USB SPI programmer and will see if I can cajole it into working with these chips.

  10. #20

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    I don't have a working adapter to pull the EEPROM contents but based on the code from the attempted Linux driver I have created a small program to generate EEPROM values with a randomly assigned MAC address. I've attached the C++ source and a Windows .exe

    It generates a random MAC address, a manufacturer time stamp based on the current time, and a checksum value which should pass the driver test.

    One solution would be to use this generated EEPROM content to patch the DOS packet driver to use it instead of reading it from the hardware. It would take some reverse engineering of the driver but is theoretically possible.
    Attached Files Attached Files

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