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27cxxx eprom switcher

Discussion in 'Electronic Design' started by mark krawczuk, Feb 7, 2007.

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  1. hi , can anyone point me in the right direction for a eprom switcher
    schematic ?

    this is what i want to do :

    i have a engine ecu which contains a 27c128 eprom , i want to be able to
    switch between 2 .bin files (maps) while the engine is running i.e on
    the fly . i presume i will have to use a 27c256 eprom .?

    any help appreciated.

    mark k
  2. Rich Grise

    Rich Grise Guest

    Do not do this, because if you do, people could die.

    If you want to change your car's ECU program, put it in the shop, up on
    the rack, pull out the old EPROM, plug in the new, presumably pre-tested,
    EPROM, test the new EPROM and its functions, THEN it could be safe to let
    the car down off the rack.

    Switching the ECU program while running is suicide, which I'm not telling
    you not to do (see "Darwin Effect"), but it's terribly important to
    caution you against taking any innocent bystanders with you when you lose
    control of the car.

    Tell the teacher, "I refuse to do this assignment because it endangers the
    life and limb of innocent people."

    Good Luck!
  3. Ensure that you have a giant spike which is driven into the ground by
    explosives during the transfer period to ensure that your vehicle is safe
    during the transfer.
  4. artie

    artie Guest

    Ooh, sounds like fun...

    You should be able to just switch the top address bit on a c256 to
    select which c128 image you're feeding to the ecu.

    Ignore those worrywarts -- go for it. What's the worst that can
    happen, eh?

    Have someone taking pictures, video -- from a distance.
  5. Eeyore

    Eeyore Guest


    If you can indeed separate the map from the code that might work.

  6. Sensibly now, Yes you can just switch the MSB on a 256, but I wouldn't
    advise doing it while the engine is running.You will probably crash the ECU,
    maybe damage the engine?. Absolutely no problem doing it with the engine
    If the eprom just contains a map, and no CPU executables, then you could do
    it with the engine running ( your risk!) but you would need to synchronise
    the switch with some logic with the CPU. Put the switch input onto the D of
    a D type and clock it with one of the system clocks from the CPU.....
  7. Well, if it is just for yourself, solder 2 on top of each other and switch the
    OE lines (you'd have to peal of the bottom ones OE line from the board), and
    gate these with the board signal.
  8. James Beck

    James Beck Guest

    I did something very similar for a game that someone wanted to swap a
    lookup table during runtime. It has been a LONGGGGG time ago, but what
    I did was to use a latch to change the upper address line (swap banks)
    only during the rising edge of /CS. That way I knew the CPU was doing
    something else and, in this case, just swapping the lookup table didn't
    blow anything up.

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