Any progress in modchip reverse engineer??

[patroclus02]

Any progress here?

or in the Cd burning contest??

I'm still waiting to get a logic analyzer to work on modchips, and try to make another way to boot up games.

Maybe replace the BIOS would work (well, I think that it must work, with one exception : the CD board has an internal command that rejects a copy)

 

[Pinchy]

heres some info:

http://www.crazynation.org/SATURN/saturn.htm

Ive got some vhdl wrote thats got most stuff implemented but I still want to understand what exactly the commands mean thats sent to it and how the sector/position is encoded into them.

Found the data commands sent from MPU-> cd DSP on the cd board and there not exactly the same as the datasheets. the docs say 12 bit command is sent but the saturn one uses only 8 so I havent figured how it correlates to the main commands sent from the saturn mobo.

apparently the cd dsp has a smaller number of registers then the hd49235.

 

[patroclus02]

I worked some time ago on trying to capture all commands sent from Saturn to CD (pin 18 in your pinout, p60 64337 I/O DATA), and the filtering the modchip does to it.

But I have no logic analizer and used a homemade "logic analyzer" using LPT port (so slow, and it misses some data randomly). Anyway, I got much of the commands in a single capture (but some are corrupted).

Data stream sent by pin 3 in your pinout, is just to fast to get captured by this method.. This two signals are changed by modchip, so I suppose it is enough to understand them in order to get lots of info.

I will read your web carefully. Thanks.

(by the way, I'm spanish and maybe I call things different.., but what is MPU and cd-DSP? Sure I know what I'm talking about, just call things different. Thanks for the info!!)

 

[Pinchy]

Ive figured most everything how the modchip works and how the cd interface works.

Cyberwarrior hooked me up with some nice example code to read sectors from a disc which helped tremendously.

Ive updated the saturn cd info page:

http://www.crazynation.org/SEGA/Saturn/cd_tech.htm

heres a text file showing the commands and some notes to help explain whats going on:

http://www.crazynation.org/SEGA/Saturn/files/command_log.txt

Ive got some modchip vhdl code that is partially working, it at least returns ring sector data that saturn accepts. I just need to properly take over the command and status data. Im not sure if I can fit all that into the cpld im using (256cells).

I also finally finished my dev cart. No more lousy comms link

http://www.crazynation.org/SEGA/Saturn/cart.htm

Still has very slow imho dev cycle. You have to wait for those lousy splash screens. I made some modifications to the AR protocol so thats its a little more robust. And modified(debounced) the joystick routine so that when you enter text in you dont tttyyyppee llliiikke tthiss.

I use the cypress Fx2 chip for USB but with some modification to the vhdl(and possibly the ar firmware) you should be able to use a parallel port.

 

[RockinB]

Crazy stuff, Pinchy!

This dev cart looks very interesting. Is the PCB selfmade?

Do you use a patched AR firmware which resides in those 2 flash chips?

I got an FPGA board and maybe I'll try to connect that to Saturn sometimes.