Memory
Allocation
For larger memory pictures, you need
to
allocate more memory. Here is a formula for
calculating memory requirements in general:
bytes per line
* lines
in
playfield * # of bit-planes
Thus, if the wide playfield described
in
this section is formed from two bit-planes, it
reqUIres:
80 * 200 * 2 = 32,000 bytes of memory
Recall
that
this
is
the memory requirement for the playfield alone. You need more
memory for any sprites, animation, audio, or application programs you are using.
Selecting
the
Display
Window
Starting
Position
The
display window starting position is the horizontal and vertical coordinates of the
upper
left-h2l.nd
corner of the display window. One register, DIWSTRT, holds both the
horizontal and vertical coordinates, known as HSTART and VSTART.
The
eight bits
allocated
to
HSTART are assigned
to
the first 256 positions, counting from the leftmost
possible position. Thus, you can
start
the display window
at
any pixel position within
this range. .
Playfield Hardware
69
To Next Page
Loading...
