Reading Emcotronic M1 roms

I have sucessfully read the roms from the M1 mainboard using the TOP853 rom programmer.

The process was surprisingly smooth. I was prepared for all sorts of problems along the way, but it just worked. Uncanny...

I ran the TOP853 software from virtualbox to read the roms into .bin files and then i used bokken from the ubuntu repos to parse and look at the files. This is how I did it:

Open the chip select dialog in TOP853.

Type in 27256 and select EPROM.

Select a long delay for reliable reading.

Start reading the chip into the buffer.

Save the buffer to .bin file.

 

Open bokken and select the .bin file.

You can browse the dis-assembled code.

 

You can view the strings table.

The plan ahead now is to buy a few replacement roms (modern variants with identical pin-out) and copy the images over and see if they work. Once they work I can start modifying the code slightly.

Figuring out what to change in the code and where might seem harder than it is. I thought about ho to do it and I came up with the idea that the strings tell me something about what the code does, so all I have to do is to follow the strings and see which code pushes the strings around. Next I just identify which strings relate to which functions (such as loading/saving MSD data) and hijack those routines by jumping to an unused location where I have some space for my own code.

Well in theory at least.