a vblank basic question

a vblank basic question
by Anes on 2005-12-09 (#7303)

when does vblank exactly hit?
i mean after rendering a pre scanline, then 240 scanlines and a rest one. Does it hit at the end of the rest one i mean cc = 341 or at cc == 0 of the next one?

if this cuestion is to lame please membler/s delete it.

by Celius on 2005-12-09 (#7310)

Well, I think it's just at 0 of the next one. Like, I'm really not sure about what you're asking, I'm confused. You seem like you know the NSTC frame format, but I don't know what you're asking. Like if it begins at the very bottom or the very top of the screen? Like the idle scanline after 240 + 341 PPU cycles? or 0 of the 20 scanlines of Vblank? I probably sound really retarded right now. Can you possibly reword your question? I'd be happy to help.

by Roth on 2005-12-10 (#7312)

I think the wrap-around time is included in the V-Blank. The initial hit is at the top, so 0 would be where it starts... of course, I'm not 100% positive, but I'm just assuming this after having read the second paragraph in the first post on this forum:

Quote:
But a scanline consists of not only the time it takes to scan the electron beam across the picture tube, but also the time it takes for the beam to return to the start of the next line (the horizontal blank, or retrace)

http://www.atariage.com/forums/index.ph ... opic=27188

I would assume it is the same for V-Blank.

by Muchaserres on 2005-12-10 (#7320)

Yeah, you're right. It starts at the very end of cc 341, or at the very beginning of the next scanline, cc 0. It's just the same thing from different points of view.