o How collisions between objects are sensed
o How system direct memory access
(DMA)
is
controlled
o How interrupts are controlled and sensed
Video
Priorities
You can control the priorities of various objects on the screen
to
give the illusion of
three dimensions.
The
section below shows how playfield priority may be changed rela-
tive
to
sprites.
FIXED SPRITE PRIORITIES
You cannot change the relative priorities of the sprites. They will always appear on the
screen with the lower-numbered sprites appearing in front of (having higher screen prior-
ity than) the higher-numbered sprites. This
is
shown in figure 7-1. Each box represents
the image of the sprite number shown in
that
box.
I
7
I
6
I
5
-
I
4
-
I
3
l-
I
2
ro-
I-
1
-
0
r--
!-
Figure
7-1:
Inter-Sprite Fixed Priorities
198 System Control Hardware
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