Atari display list

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3 total messages Started by Dale Chavdiere Fri, 21 Sep 1984 19:51

#385

Author: Dale Chavdiere
Date: Fri, 21 Sep 1984 19:51

8 lines
1181 bytes

I am having trouble with modifying the display list to mix graphics and text
modes.  Specifically, I have written a slot machine game using the PM Animator
software.  I poked memory locations used by the display control chip to put
some graphics mode 2 lines in a graphics mode 7 field.  The program works fine
on my 800 using a monitor for display.  If I use a normal TV the display rolls
vertically.  Question;  Am I sending too many lines to the display chip?  Is
there a memory location to control the number of scan lines sent to the display?I believe the monitor just ignores the extra lines.

Re: Atari display list

#384

Author: James Van Ornum
Date: Sun, 23 Sep 1984 00:58

9 lines
967 bytes

<>
The display list itself determines how many scan lines are to be generated.
Thus if you modify the display list, you need to redetermine how many
scan lines are defined and make adjustments in the list to keep that number
to about 216.  "Your ATARI Computer" by Ion Poole has a lot of information
about customizing the display list.

-----------------------
	James Van Ornum, AT&T Bell Laboratories, inhp4!houxu!jhv

Re: Atari display list

#393

Author: Dan O'Connell
Date: Wed, 03 Oct 1984 16:21

8 lines
1080 bytes

In order to make a custom display list work best on a normal TV,
you should have no more than 192 scan lines in total.  If you have
more than that, rolling may occur on a TV because of the overscan.
I can not recall how many scan lines each line of graphics takes,
but I think each line of gr.7 is 2 scan lines, and each line of
gr.0 is 8 scan lines.
Another problem that could cause the rolling on the TV is that
if the screen data crosses a 4 K boundry, weird things happen.

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