[atari7800] direct indirect headers
- From: <bob.montgomery@xxxxxxxxxxx>
- To: <atari7800@xxxxxxxxxxxxx>
- Date: Fri, 11 Apr 2008 10:52:57 -0600
Hi all,
Re-reading the Maria doc again, this has me a bit confused:
Cut-n-paste here, from the section explaining 5-byte headers:
ADDRESS (A15-A0) - Address of graphics information.
MODE BYTE: WM - Write mode bit.
0 => 160x2 or 320x1
1 => 160x4 or 320x2
IND - 0 => Direct mode.
- 1 => Indirect mode.
PALETTE (P2-P0) - Refers to color palettes 0-7.
WIDTH (W4-W0) - 2's complement of width.
Specifies number of bytes of
graphics data to fetch: values
1-32.
HORIZONTAL
POSITION (H7-H0) - X location on the screen where left
edge of graphics is to be placed.
0-159 => Visible
160-255 => Not visible.
Wrap around occurs at 255/0
boundary.
This would seem to imply...that you can use a 5-byte header for direct
mode?
And if not, how *does* Maria interpret the 2nd byte of a header of this
form:
%W1000000
?
If you *can* use a 5-byte header for direct sprites, a few questions:
Couldn't you then have direct sprites with a width of 32?
Couldn't you then set the write mode for direct sprites, um, directly?
Rather than having to use a dummy 5-byte indirect header?
Thanks,
-Bob
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