Table 3-6: Play
field
Memory Requirements
Number
of
Bytes
Picture
Size
Modes
per
Bit-Plane
320 X 200
Low-resolution, 8,000
non-interlaced
320 X 400
Low-resolu tion, 16,000
interlaced
640 X 200
High-resolution,
16,000
non-interlaced
640 X 400
High-resolu tion, 32,000
interlaced
A normal low-resolution, non-interlaced display has 320 pixels across each display line
and a
total
of 200 display lines. Each line of the bit-plane for such a display requires 40
bytes (320 bits divided by 8 bits per byte
= 40).
A low-resolution, non-interlaced playfield made up of two bit-planes requires 16,000
bytes of memory area.
The
memory for each bit-plane must be continuous, so you need
to
have two 8,000-byte blocks of available memory. Figure 3-7 shows an 8,000-byte
memory area organized as 200 lines of 40 bytes each, providing 1
bit
for each pixel posi-
tion in the display plane.
42
Playfield Hardware
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