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• Second Log: Research Gathered So Far.

  Colton • 11/09/2020 at 04:22 • 0 comments

  From reading the DSP datasheet (CXD2500BQ) and other documents I have roughly figured out the way a CD is read. First the laser is focused onto the CD and then the table of contents is read. Using the table of contents, the CD reader can then seek to the track on the disc using the absolute timecode. A seeking operation starts by repeatedly jumping tracks while keeping an eye on the timecode. A track in this context is not an audio track, but the tracks between the center and the outer rim of the disc of which there are 22188 on a standard 12 cm CD. When the laser is close enough to the desired timecode, the track adjustment is made to focus it onto the desired track. If it landed a little bit before the desired track the output is muted until the disc rotates to the desired area and the correct data is read. I have not yet figured out exactly how to operate the DSP but I am now closer to figuring it out.

  As for the CDROM decoder (CXD1196AR), I plan on connecting it to a SNES when I can obtain one. It should be as easy as connecting the 8 data pins, read write strobes, address select pin and interrupt pin directly to the expansion port pins. The polarity of the interrupt pin on the decoder is selectable according to the signal on another pin so if need be I can set it accordingly. Then I can burn the BIOS file onto a cartridge and run the self check. If my wiring is sound, the SNES doesn't check anything else and my decoder chip isn't dead then the CDROM Decoder test should pass.

• First Log: Game Plan

  Colton • 11/06/2020 at 05:50 • 0 comments

  For the time that I've been obsessing over the SNES SuperDisc, I have learned a lot about the console. Thanks to efforts to emulate the console I know the communication protocols used to communicate to the CD-ROM, I know the memory map of the cartridge and the I/O ports used on the expansion bus and a lot of other info. In fact, I know pretty much all there is to know about the console. The only thing I don't know is how the "Mechacon Controller" commands the actual CD-ROM drive to do things. This project is to document my efforts to reverse engineer the communication protocol between the DSP IC and the "Mechacon Controller" and then build out the rest of the console from there. Since all of the other parts are known and in my possession it should almost be as simple as exposing the decoder IC and whatever "Mechacon Controller" I come up with to the right I/O ports on the expansion bus and then creating my own boot cartridge with the BIOS rom that was dumped for the console a while ago. I will post all of the sources that I have pulled information from in the details of this project.

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