Talk:PPU rendering
0=blank vs. 0=active
There are two different conventions:
| 0=active | 0=blanking | Description |
|---|---|---|
| 261 or -1 | 20 | Pre-render scanline |
| 0-239 | 21-260 | Active picture |
| 240 | 261 | Post-render scanline |
| 241-260 | 0-19 | Vertical blanking |
You're using the 0=blanking convention. But more often on the BBS and elsewhere on this wiki, I've seen 0=active. The PPU power up state appears to agree with 0=active, as do the (X, Y) coordinate displays in the debugger of FCEUX and Nintendulator and the VCOUNT register on the Game Boy ($FF44) and Game Boy Advance ($04000006). The 0=active convention makes it easier to consolidate discussion of NTSC, PAL, and PAL clone timing as well. --Tepples 20:15, 3 April 2011 (UTC)
- Ahh, ok. I was just simply going off of what's in Brad Taylor's docs. The 0=blank method didn't make a lot of sense to me either, as does some of the other stuff in this doc (The shift registers make more sense if they shift left rather than right). I'll adjust this. --Drag 20:47, 3 April 2011 (UTC)
I think at some point, it would be worthwhile to document how the PPU outputs the vertical/horizontal sync signals. If for nothing else than to satisfy my own curiosity. --Drag 05:30, 6 July 2011 (UTC)
Garbage nametable byte
Before each sprite's patterns are loaded, at x=257, 259, 265, 267, ..., 313, 315, there is a garbage nametable fetch. Has anyone discovered a pattern to these fetches' addresses that, say, a mapper could use? --Tepples 16:07, 6 July 2011 (UTC)
