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Posted Fri Mar 24, 2017 4:37 AM
Posted Fri Mar 24, 2017 8:52 AM
Ok, you need to grab a copy of the Stella Programmer's Guide, and read that. Seriously, Go grab and read. We'll wait.
if that's TL:DR, then basically:
* Start thinking not in terms of a whole screen in memory, because that doesn't exist..
* a VCS programer thinks in individual scanlines.
* envision a player as a part of a scanline that is output from the TIA.
* On any given scanline, there can be the background color, the playfield, two players, two missiles, and a ball.
* so in essence, any of these items are vertical bands that, given that you properly do your vertical sync, stretch from the top of the screen to the bottom. Meaning:
* they can be as tall as the screen.
* Players and their missiles can be clocked out in one of several sizes, 1, 2, 4, or 8 pixel clocks. see NUSIZ in the Stella Programmer's Guide.
* Once they've been output, they can be re-used.
* Most easily this means you can re-use a player on a different scanline, to give the impression of more players on screen than normally possible.
* If you need more than two players on a line, you then need to switch to a multiplexing scheme which will display other players on alternate frames.
Posted Fri Mar 24, 2017 3:19 PM
Posted Fri Mar 24, 2017 4:18 PM
Dude, again. Read the Stella Programmers Guide. Please. Read it, and come back here.
You are creating the vertical part of the video signal in software. The TIA does just enough to handle a single line. There are 228 color clocks in a scanline, of those, 68 of those color clocks are not visible on the left side of the screen, as they are part of the horizontal blank, so there are approximately 160 visible color clocks, and the VCS divides its pixels from this.
A scanline is an individual television scan line.
Depending on the video standard, there are 262 scanlines for NTSC
and 312 for PAL.
Of those, not all of them will be visible. Atari recommends using 192 visible scanlines for NTSC, the rest are split between your vertical blank and overscan periods, which can be used for logic.
Posted Sat Mar 25, 2017 3:07 AM
Edited by funkheld, Sat Mar 25, 2017 4:48 AM.
Posted Sat Mar 25, 2017 8:31 AM
8 bits wide by any height you want. Also, you can widen the bits with one of the registers (NUSIZ0)- this will make your player wider, but no more defined.
As designed, Atari can only display 2 players. It will also display those players in double or triple if you want- again by changing register (NUSIZ0)
Note- there are many tricks to get it to display more than this, but think you would benefit from going through this tutorial first:
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