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Atari XL User Manual

Atari XL
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Page #183 background image
Advanced
Graphics
171
Lines
200
to
240
set
up
the
characters
for
the
titles,
which
are
converted
to
internal
code
and
IJO
KEd
into
display
memory
by
subroutine
500.
The
characters
are
put
into
display
memory
starting
at
the
top,
and
the
variable
MEM
keeps
track
of
the
position
in
memory
of
each
string
of
characters.
Finally,
the
picture
is
drawn
in
the
usual
way
by
lines
300
to 340.
You
can
use
the
principles
covered
here
to
create
your
own
mixed
mode
displays,
by
observing
the
following
rules.:
1
Start
with
the
display
list
of
the
mode
which
uses
the
most
memory
(in
our
case
this
was
mode
8).
See
Appendix
5 for
memory
requirements
of
the
various
modes.
2
Change
the
codes to
create
text
for
labelling
in
the
appropriate
part
of
the
screen.
3
Calculate
the
number
of
scan
lines
required
for
the
new
display,
and
if
greater
than
192
transfer
the
jump
from
the
end
of
the
display
list
to a
point
such
that
the
display
requires
no
more
than
192
scan
lines.
4
Calculate
the
memory
requirements
for
each
text
mode
display
block,
and
POKE
the
internal
codes for
the
characters
into
display
memory.
5
Draw
the
mode
8
picture
in
the
normal
way.
These
rules
and
some
patience
are
all
that's
needed
to
create
a
very
complex
mixed
mode
display.

Table of Contents

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Atari XL Specifications

General IconGeneral
Release Year1983
CPUMOS Technology 6502C
GraphicsANTIC, GTIA
SoundPOKEY (4 channels)
StorageCassette tape
PortsCartridge
Operating SystemAtari BASIC
CPU Speed1.79 MHz
RAM64 KB

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