Program a MC68705U3S

Discussion in 'General Electronics Chat' started by shorteddiode, May 20, 2013.

  1. shorteddiode

    Thread Starter New Member

    Apr 6, 2013
    6
    0
    I have a customer that brings me his table top arcade games for repair. They are machines like "Measure your love-ability, Fortune telling etc." Right now I have 3 fortune telling machines that all have the same problem and after doing voltage checks I believe the problem is the MC68705U3S, I think the program is corrupted.
    If I find one with a good program how difficult is it to copy the good program to reprogram the bad ones? Also, what programer do you recommend?
    I do TV, and Audio repair so I don't believe I would use a programer much so I am looking for a low cost but dependable programer.










     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,367
    You have a number of challenges facing you:

    1) Is the code read protected?
    2) Would you be infringing on someone's copyright?
    3) Can you find replacement MC68705U3S?
    4) Can you find someone with the right hardware to program a new chip?
     
  3. shorteddiode

    Thread Starter New Member

    Apr 6, 2013
    6
    0
    I don't know if the code is write protected,
    I can find MC68705U3S,
    would it be a copy right infringement if I am using the program on the machine the bad one came out of?
    What type of hardware do I need to read a good chip and re-program the bad chip?
    I would like to be able to read and write the chips in my shop
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,367
    It has been too many years since I last programmed a MC68705.
    I will have to look into this in order to get you an answer.
     
  5. shorteddiode

    Thread Starter New Member

    Apr 6, 2013
    6
    0
    Thanks guys,,,,Is there any good reference books I can read on the subject?
     
  6. Meixner

    Member

    Sep 26, 2011
    116
    21
    Maybe the datasheet but it might not be much help.
    The 68705 is an older processor, I dont think they could be copy protected. A quick search on Ebay didnt turn up any used programmers for sale. I would suggest if you find a working machine swap the processor to see if it fixes the problem. If it does post back here and fill in your location. Maybe someone near you has a programmer that will read your part and would be willing to copy some for you.
     
  7. MrChips

    Moderator

    Oct 2, 2009
    12,449
    3,367
    Looking over the datasheet of the MC68705U3, this is a 40-pin DIP with 3776 bytes of UV-EPROM. It is normally programmed using a built-in bootstrap code and a preprogrammed EPROM. It requires +21V at Vpp for programming. A programmer can be built using the circuit provided in AN857/D.
    I have not found AN857/D after doing a quick search on the internet but I believe I have a picture of the circuit schematic in numerous Motorola documentation.

    Normally, there is no way to read out a preprogrammed MCU. However there is loop hole as explained by Matthieu Benoit. (I have not read it through completely).

    The catch is you have to be able to program a 2732, 2764 style UV-EPROM. I abandoned mine many decades ago.
    I don't know how many people can still program a UV-EPROM.

    http://matthieu.benoit.free.fr/pdf/How_to_read_the_MC68705U3_EPROM.pdf

    http://matthieu.benoit.free.fr/pdf/MC68705U3_Bootstrap_ROM_Listing.pdf
     
    Last edited: May 21, 2013
  8. shorteddiode

    Thread Starter New Member

    Apr 6, 2013
    6
    0
    Thanks everyone, looks like if the EPROM is the problem the machines will just be put on a shelf and used for parts.
    Thanks again
     
  9. kb50

    New Member

    Oct 27, 2013
    5
    1
    Since the product is probably too old to even find parts, their only hope would be finding another used machine, with a different problem and swapping the computer board entirely. I have one of these chips, from a AP snack vending machine. I suspect there is no way to even reprogram it, even though I do have a UV eraser box. I however lack any sort of programmer for it, and suspect one would have to custom build a programmer, thats if you could even write a useful program for it. Mouser Electronics and Jameco electronics might have a way.
     
Loading...