Subject: RE: [stella] VBLANK or VSYNC first? From: Nicolás Olhaberry <nolh@xxxxxxxxxxxxx> Date: Mon, 29 Oct 2001 23:07:47 -0300 |
> 1. The docs all show VSYNC as the top of the frame (3 lines) and then 37 > lines for VBLANK. So isnt the scanline counter reset when VSYNC is written > to, not when it is turned off? Doing it as you suggest would be 3 lines > too late, yes? You can restart the counter when VSYNC is turned on or off, it´s just a matter of taste, you´re gonna have those 3 lines either way (at the start or at the end of the frame). Anyway, since those lines will not display anything, is not really important. > 2. What is the beam counter actually used for? Only for reference? If I > understand it, RSYNC controls this, but RSYNC seems hardly ever used :/ The TIA handles all the horizontal sync internally, but if you want to write an emulator, you have to do it yourself, of course. A few examples: you can´t increment the scanline counter until the horizontal counter reaches 228, another... when RESP0 is written to, you use the counter to know where in the scanline is going to be displayed, etc... As you can see, you´re going to use it all the time ;-) Bye, Nicolás. - Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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