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Does anyone know the means by which software synchronizes frames with the shutters on the 3-D glasses?

I thought that maybe software used one of the signals going out of the card slot to trigger a shutter flip, but I looked at the schematics and there aren't any "interesting" signals that could be used. I thought maybe the CE2#, but then I ran some 3-D games in MesaDX trapping for writes to port 0x3E, but there were none of interest. The only other signal of interest is CONT, but I think that has something to do with soft-reset (reset when pressing the SMS's Reset button). I also thought that maybe a data write between 0x0000 and 0x7FFF might be used (since the game contains ROM at those addresses and there's no danger of writing over code). I used MesaDX to trap for writes to those addresses, but again it was a dead end. I don't think I/O writes can work, since IORQ# isn't sent out through the card port.

So, does anyone have any ideas?

--
Eric Quinn

As I recall, 0x8000 was the 'hot spot' used to toggle the glasses: it detects a write to that location and uses a bit from the value written to determine which shutter to keep open.

This works because the device in the card slot can 'see' all bus activity, even though chip enable isn't sent to the card.

I may totally have this dead wrong, it was posted here at one point but has since been scrolled off the message log (We've really got to start writing things down). But I'm fairly sure it was 0x8000 used to toggle.

Quote

> As I recall, 0x8000 was the 'hot spot' used to toggle the glasses: it detects a write to that location and uses a bit from the value written to determine which shutter to keep open.

> This works because the device in the card slot can 'see' all bus activity, even though chip enable isn't sent to the card.

> I may totally have this dead wrong, it was posted here at one point but has since been scrolled off the message log (We've really got to start writing things down). But I'm fairly sure it was 0x8000 used to toggle.

Yes, thank you. I was able to confirm, using MesaDX, that Space Harrier 3-D and Maze Hunter 3-D both write to 0xFFFB the data 0x00 or 0x01 every other frame.

--
Eric Quinn

Author	Message
Eric R. Quinn Joined: 18 Sep 1999 Posts: 498 Location: Portland, Oregon USA	3-D Posted: Wed Jun 06, 2001 9:13 pm
	Does anyone know the means by which software synchronizes frames with the shutters on the 3-D glasses? I thought that maybe software used one of the signals going out of the card slot to trigger a shutter flip, but I looked at the schematics and there aren't any "interesting" signals that could be used. I thought maybe the CE2#, but then I ran some 3-D games in MesaDX trapping for writes to port 0x3E, but there were none of interest. The only other signal of interest is CONT, but I think that has something to do with soft-reset (reset when pressing the SMS's Reset button). I also thought that maybe a data write between 0x0000 and 0x7FFF might be used (since the game contains ROM at those addresses and there's no danger of writing over code). I used MesaDX to trap for writes to those addresses, but again it was a dead end. I don't think I/O writes can work, since IORQ# isn't sent out through the card port. So, does anyone have any ideas? -- Eric Quinn

Heliophobe Site Admin Joined: 25 Oct 1999 Posts: 2029 Location: Monterey, California	Posted: Wed Jun 06, 2001 9:45 pm
	As I recall, 0x8000 was the 'hot spot' used to toggle the glasses: it detects a write to that location and uses a bit from the value written to determine which shutter to keep open. This works because the device in the card slot can 'see' all bus activity, even though chip enable isn't sent to the card. I may totally have this dead wrong, it was posted here at one point but has since been scrolled off the message log (We've really got to start writing things down). But I'm fairly sure it was 0x8000 used to toggle.

Zoop Joined: 24 Jun 1999 Posts: 1732 Location: Paris, France	It is 0xFFF8-0xFFFB nt Posted: Wed Jun 06, 2001 11:07 pm
	Quote > As I recall, 0x8000 was the 'hot spot' used to toggle the glasses: it detects a write to that location and uses a bit from the value written to determine which shutter to keep open. > This works because the device in the card slot can 'see' all bus activity, even though chip enable isn't sent to the card. > I may totally have this dead wrong, it was posted here at one point but has since been scrolled off the message log (We've really got to start writing things down). But I'm fairly sure it was 0x8000 used to toggle.

Eric R. Quinn Joined: 18 Sep 1999 Posts: 498 Location: Portland, Oregon USA	Re: It is 0xFFF8-0xFFFB Posted: Wed Jun 06, 2001 11:20 pm
	Yes, thank you. I was able to confirm, using MesaDX, that Space Harrier 3-D and Maze Hunter 3-D both write to 0xFFFB the data 0x00 or 0x01 every other frame. -- Eric Quinn

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