Saturn switchless mod IC behaviour

Started by tassian, April 11, 2004, 09:35:01 PM

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First of all: the idea for the Saturn switchless mod is just ingenious, I love it! :-)

I'm planning on modding my European Saturn to play Japanese games as well, so I'm going to use the additional input/output 1 or 2 of the 74157 to feed GND or +5V to JP12/JP13 (only a slight modification to the description of the switchless mod), no problem so far. When playing with the multimeter I've noticed that 1Y is only connected to 1A as long as there's +5V on the select line. As soon as select is connected to GND, 1Y is back on 1B (and the other way around). I'm planning on using the reset button of the Saturn for switching regions as proposed in the switchless mod description. When "multimetering" the reset button, I have a constant +5V on one pin which changes to 0V while the button is pressed. As soon as the button is released, it goes back to +5V. If I connect the select line of the 74157 to this pin of the reset button, the outputs nY of the 74157 are only switched between nA and nB as long as the reset button is pressed. After releasing it, there's a constant +5V on the select line of the IC again. My question is: since there's normally a constant +5V for the select line and only a 0V while reset is pressed, is this really sufficient to switch the Saturn to a different region? E.g. if you solder the nYs to the Jumpers of the Saturn in a fashion that you have a European configuration if select is +5V and a Japanese one if select is 0V, the Japanese configuration is only there for a few nanoseconds after reset is released. Is this sufficient? Thanks a lot in advance for clarifying this! I'm not an electronics guy at all, I've only learned about the behaviour of the 74157 by reading Philips datasheets and by reading the excellent description on gamesx. So please be patient if this question is stupid. :-)

One more thing: I'm wondering if this mod can be enhanced so that you can actually switch between EUR, US and JAP with one switch. Any ideas? TNX!



I have found a way that might work: I'm planning on using a 74191 (switch triggered, resetable binary counter) to achieve all possible region switches. Features that would be possible using the 74191 are:

- Open CD-drive lid can reset region code to a code of your choice (using a default that can be chosen by setting certain input pins of the 74191 to 0V or +5V)
- Reset switch cycles country codes

What I still need to figure out is: I only want to change between JAP, EUR and US so I need to figure out a way to get rid of all jumper combinations of 0V and +5V that can be set for jumpers JP6/7, JP10/11 and JP12/13 that would set the Saturn into an undefined state or a region that makes no sense (isn't used). E.g. all jumpers set to 0V or +5V wouldn't make a lot of sense (it may even damage the Saturn?).

I'll keep you posted if I find out something new. If you have any ideas, please let me know.



Will you guys include some photos when you do the mod? I am still a little confused on how to do this mod. I saw the Gamesx photos, but I have a US Saturn.