Sample Data
for
4 Pixels
1
1
1
o
o
1
o
o
1
o
o
1
o
1
1
o Data in Bit-Plane 5 - Most Significant
o Data
in
Bit-Plane 4
1 Data in Bit-Plane 3
1 Data in Bit-Plane 2
o Data in Bit-Plane 1 -
Least
Significant
L Value S - COLORS
1--
__
----
Value
11
- COLOR11
1----------
Value
18-
COLOR18
'-------------
Value 28 - COLOR28
Figure 3-4: Significance oLBit-Plane
Data
in
Selecting Colors
You also have the choice of defining two separate playfields, each formed from up
to
three bit-planes. Each of the two playfields uses a separate set of eight different colors.
This
is
called dual-play field mode.
Forming
a
Basic
Playfield
To
get you started, this section describes how to directly access hardware registers
to
form a single basic playfield
that
is the same size as the video screen. Here, "same size"
means
that
the playfield
is
the same size as the actual display window. This will leave a
small border between the play
field
and the edge of the video screen.
The
playfield usu-
ally does not extend
all.
the way to the edge.
To
form a playfield, you need to define these characteristics:
o Height and width of the playfield and size of the display window
(that
is,
how
much of the playfield actually appears on the screen).
o Color of each pixel in the playfield.
Playfield Hardware
33
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