SpritesMind.Net

Yes, I don't remember where that is in the docs offhand, but Sega recommends setting the SOURCE to one word past the start, doing a DMA of N words, then writing the FIRST word using the CPU. That avoids any corruption in the vram. They even provided a snippet of example code that did that. Now if I ...

Orion_ wrote:I guess this could be a little emu protection code

You're a little evil ....

But now the trick is exposed ...

The MEGA-CD really deserves a WIKI of some sort ...

Find a copy of the FLUX ROM http://www.youtube.com/watch?v=Oswpqv22TIg

You can disassemble it and see how it works.


It boots from Cartridge and can control the CD unit completely.

I put some thought on this and the purpose of this boot modi could be manufacturing optimization. This could be meant to be used at the factory to boot a diagnosis cartridge....

Is this before or after the rest of the CD BIOS has been initialized? It's very interesting... I may want to do some checking myself. And here I thought we'd figured everything out on the CD.

Actually ElBarto and a few other people were talking about it in this very forum a while ago .... 8 ...

Interesting. If that's true, it's probably looking for something similar to the boot block Mode 1 is looking for, just at 0x400000 instead of 0x6000. You might try a modified version of the block in the Mode 1 example and see if that runs. That would make yet another way of booting for the MD. :D ...

What are you trying to do? Most all of this is already well-known. If you're trying to init the CD while a cart is running, that's already done. I released code for Mode 1 CD support a couple years ago (example and code still available here and elsewhere).

If the cart is not asserting the CART ...

Offset 0 1 2 3 4 5 6 7 8 9 A B C D E F

00400000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00400010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00400020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00400030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00400040 00 00 00 00 00 00 ...

MICON > Controls the low level tasks related to disc reading such as read disc table of contents, jump tracks, keep the data flowing during playback and other boring housekeeping tasks related to CD playback. Usually (on CD players) it's connected to another chip which controls the panel keys and ...

There's a few "generic" parts that form a CD Player circuit:

RF Frontend > Interfaces the laser diode and photodiodes with the micon and dsp, provide the PLL loop that controls disc spin speed and keeps lens focused, following commands given by the micon chip

DSP: Correct basic errors on the data ...

can you explain it ? I don't understand what you mean.

I don't know the software specifics, but I am sure you do, since you're one of the scene specialists on MEGA-CD...

Well I was looking at the documentation you guys put out some years ago and there were mentions of sets of 4 bit "instructions ...

I don't think the lines I want to "spy" are analogs:
/INT, CDCK, DBx,WFCK, SBSO, ESXK, .....

From what I understand, it's the data for the LC8951 (to manage the DATA side of the CD Drive) and the CXD2500AQ (to manage the AUDIO side of the CD Drive)
Perhaps I'm wrong, I just (re)started to check ...

I'm about to put out a new set, which restores the original behavior of the cartridge booting mechanism you guys discovered a while ago...

I used the TMSS code that was on the bios as data to show the logo. That disrupted the cartridge boot mechanism.

Also the new set of BIOSes will have a routine ...