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Pengwin

Question about DLI's

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I'm a little confused about Display List Interrupts.

 

If I have a display list as follows:

 

 

 DATA($7000)
 [
   112,112,112,72,$94E8
   8,8,8,8,8,8,8,8,8,8,8
   8,6,6,6,6,135,6,7
   65,$7000
 ]

 

Should the interrupt effect the third to last line (135) or the following line (6)?

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DLI's happen on the last line (or only line) for the specified mode, allowing you to make changes before the next line starts. Usually a WSYNC is used to align with the HBLANK area.

 

http://www.atariarch...ere/chapt05.php

 

Right, so if I have a displaylist containing:

...,135,2,...

Then, if I make a colour change, it won't effect the mode 7 line that the interrupt is on, but it will effect the mode 2 line following it. Is that right?

 

Sorry if these are basic questions, but I've not really dealt with interrupts before.

Edited by Pengwin

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As long as you wait long enough. If you make the change immediately in your DLI routine, you'll see it partway into your last mode 7 line with a lot of jitter since which cycle the DLI will be serviced on is dependent on the length of the current instruction. WSYNC gets you to the end of the line.

 

Just for fun, make your DLI both ways. Change the color before and after a STA WSYNC and see the difference.

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