Is this possible with IRQs? I used to think it was possible with the Sprite 0 hit, but I read somewhere that the sprite 0 hit doesn't trigger on the right side of the screen or something (what's up with that?). I guess the last way would be to used timed code. I've read about doing that here.
It seems I hae to create a cycle-timed loop. But I don't see why it needs to be 113.667 cycles. Isn't ~341 PPU cycles (meaning that the electron beam thing would already be finished with HBLANK)? Shouldn't it be timed differently so that it can get into HBLANK instead of the begginning of the scanline? I'm not sure about the exact amount of cycles to get into HBLANK is though. But even though in some NTSC TVs the rightmost ~5 arn't displayed (happens in my TV and some others) anyway so you could get even more time.
So I guess my question is. Is there any other way to get into HBLANK? Shoudn't the timed code to get into HBLANK be ~85 instead of 113.667? And is it possible with the scanline IRQs some mappers have?