Section 1- Theory Of Operation; User Interface - Atari 800XL Service Manual

SECTION
I
THEORY OF OPERATION
The
Atari
800XL
W
Is
an enhanced version
of the existing ATARI Computer
Systems.
It
can be
used with
any
of
the existing
Atari peripheral
devices
used with
the
400'V600XL"V800
,M
/
1
20QXL
M
Computers.
The
printed circuit
board
contains
64K
of
RAM
,
an
operating systems
that
contains ore
1
6K
X
8
ROM
and an on-
board
Atari BASIC programming
language
I.C.
The
console contains the
keyboard
and
four
function keys
(
including
a
HELP
key), plus a RESET
key, a detachable
(
RF) TV
interface
cable, connector Jack
for daisy-chaining peripherals and connecting hand
controllers, a
single
cartridge
slot,
ore
status
LED (POWER),
a5
pin DIN
Monitor Jack, and a
parallel
bus
interface
USER INTERFACE
The
Atari
800XL
is
a
general
purpose microcomputer
that uses a
6502C
microprocessor.
The
800XL
console
is the central processing unit
for
its
respective system.
The
right side panel contains the controller jacks
that accept the Atari X-Y
joysticks and
paddle
controllers.
The
rear
panel contains the serial input/output
(SIO)
jack, the parallel bus
interface,
theRF
jack, the monitor
jack, the channel
2-3
switch, the power
in
jack, and
the
power
switch
(On/Off).
The
console has a
3/4
stroke,
56
key, alphanumeric
keyboard,
that includes special
characters
and
controls,
space bar, four
function keys,
HELP
key, and power
indicator. The
function and
HELP
keys are
discussed below.
FUNCTION KEYS
HELP
-
Returns
to
main
self-test
menu
from
individual
test
and
for future software
development
for user
"help" functions.
If
you are
familiar with I200XL
operation, this
kev
do&
noi
function the
same.
OPTION - Allows
the player
to
choose variations
of a program.
If
the
OPTION Key
is
not
depressed and
held
at the time
the
computer
is
turned ON,
the built-in BASIC
is
automatically
enabled.
If
the
OPTION
key
is
depressed and
held
at
the
same
time
the computer
is
turned ON,
the
on board BASIC
is disabled and,
when
there
is
no
cartridge or
diskette in the system,' the
5