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[Actarus]

I have read on a pdf that there are 32 pixels of hblank, is the screen 512 pixels (480+32) x 272? Can I set a hblank irq like vblank?
If yes is there a vblank zone? If yes how is it big?

Thanks for your answer

[J.F.]

The display pitch has nothing to do with blanking. Many display processors use power of 2 or similar fetch widths on the bitmaps.

[Actarus]

But I think that blank period is necessary for normal display operations. Is it correct?

[J.F.]

Yes, but that difference between 480 and 512 has NOTHING to do with it. For example, the same bitmap has no extra vertical lines (272 tall, period), but there IS a vertical blank period.

You seem to be thinking in 16 bit terms. This isn't a Genesis or SNES where you need to modify the sprites or palette or layers at certain lines. You have a framebuffer that is in 16 or 32 bit direct color which you render all at once, then make the visible frame. If you need the display to look different at line X, you simply render until you reach line X, then change the way you're rendering.