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Any progress in modchip reverse engineer??

patroclus02 - Jun 9, 2005

		patroclus02		Jun 9, 2005
			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		Jun 14, 2005
			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		Jun 18, 2005
			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		Sep 28, 2005
			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/comma... 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		Sep 29, 2005
			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.