VINT == VBLANK? - NESdev BBS

VINT == VBLANK?
by amin2312 on 2009-08-18 (#49964)

i am reading 'NTSC 2C02 technical reference',
it worte:0..19 scanlines make up the period of time is called "VINT",
Is it VBLANK?

if true,then 21..260 scanlines are render scanline,but some other documet is wrote:0..240 scanlines are render scanline,how to explain it?

by Drag on 2009-08-18 (#49966)

I think it's just a difference of terminology. Essentially, there are 240 rendered scanlines, plus a number of scanlines of vblank.

I don't think vblank necessarily comes "before" each frame, nor "after" each frame, so theoretically, depending on the programmer, the first rendered scanline could be scanline 0, or it could be whatever scanline comes after vblank.

That's just my opinion though.

by tepples on 2009-08-18 (#49967)

Some other Nintendo platforms have a "VCOUNT" register. At least in the Atlantis architecture (used by the GBA and the DS), 0 is the top rendered scanline and 159 or 191 is the bottom rendered scanline.

by Dwedit on 2009-08-18 (#49969)

On NTSC, there are 262 scanlines.
Which scanline is #0 depends on who you ask.
Some emulators refer to scanline #0 as the first visible scanline, and call the pre-render scanline #-1.

Re: VINT == VBLANK?
by Zepper on 2009-08-18 (#50004)

amin2312 wrote:
i am reading 'NTSC 2C02 technical reference',
it worte:0..19 scanlines make up the period of time is called "VINT",
Is it VBLANK?

Yes, it's the VBlank period.

Quote:
if true,then 21..260 scanlines are render scanline,but some other documet is wrote:0..240 scanlines are render scanline,how to explain it?

Personally, I count as scanline 0 the first line of VBlank, and line 21 the first line of rendering (visible field). Other folks prefer to call line -1 as the pre-rendered scanline, then 0~239 as visible lines, then 240~260 the VBlank period. Just another way of building a PPU abstraction. ^_^;;

by amin2312 on 2009-08-18 (#50007)

thank you all!