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.










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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?

 

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

 

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.

 

Thanks guys,,,,Is there any good reference books I can read on the subject?

 

Is there any good reference books I can read on the subject?

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.

 

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

 

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

 

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.