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Discussion in 'Microcontrollers, Programming and IoT' started by turboturbine, Dec 23, 2012.

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  1. turboturbine


    Mar 22, 2012
    Question, I want to backup the eproms from some HP equipment I have.
    I think I write all the data onto a CD, maybe I also reprogram then right away.
    some time ago I bought a dataman eprom programmer with the corresponding ISA card.
    This is the first time I work with eproms but luckely the software for the programmer is very easy to use and supports a lot of old eprom types.
    I also read about eraser light intensity, the time it takes to erase a eprom can be found in a datasheet.
    For so far I think I will suceed in doing the job.

    Can someone with some experience tell me how I know the data is read properly?
    How do I know I erased the device properly? Should I read out the device again and open some kind of file to see if all data is gone?
    I have read on the internet bits of data can retiurn after a too short exposure of UV, should I left the device for a day before checking it?
  2. turboturbine


    Mar 22, 2012
    I started the program in dosbox, wine did not work now, and I see blank check so that should solve one of my questions
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    You read the data simply by adressing the Eprom according to the datasheet specifications and reading data from the databus. Your porgrammer/software should handle this automatically once you told it the correc type of Eprom.
    As you noticed your programmer has a blank check. Otherwise you could read the Eprom and check the result. An empty Eprom should read all FF.
    If you re-program the Eproms with the same contents, you shoildn't have to worry about possibly not completely erased cells. They will be overwritten by the same data anyway - as long as you do not mix the Eproms and program each with the same content as before. It shouldn't even be necessayry th erase the Eprom before.
    Leaving the Eprom to itself doesn't improve the state of not completely erased cells. You ay as well check the chips directly after erasure.

  4. gorgon


    Jun 6, 2011
    In addition to what Harald said, your eprom programmer also verify your programmed data and generates a checksum for the data and over the address range you program. If you write this down when programming the eprom, you can verify it later if you think something has changed over time.
  5. turboturbine


    Mar 22, 2012
    OK I will write it down, I am a bit nervous doing it, because when it fails I have a problem.
    Luckely my programmer is very user friendly, easy to use interface.
    Yesterday I was thinking I had to solder some out also, there where 24pin devices with a sticker on it soldered on the pcb but they seem te be PROMS.
    I want to back all eproms I have, I also collect 80's computers I want to backup those bios eproms too, they are the old types luckely so they will fit my programmer.

    Did someone ever had experience with the so called BIT ROT? is it sure they all will suffer from this once? or is it not sure it will ever happend due to age? maybe the ones that loss data are defect?
    Beside that it is not a bad thing to backup them anyway.
  6. dpenelob


    Mar 27, 2013
    Hi turboturbine,

    since you wrote that you needed dosbox to test the software, I suggest
    to do the whole thing unter DOS. Those old programmers sometimes
    rely on direct access to the ports of the computer which is imho not
    possible with dosbox.

    Bit Rot is not a mystery. It simply means that the eproms will lose
    their data after some time, maybe due to radiation that paritally erases them
    or such.

    Best regards,
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