Fiiiir^
1-8
li aji lllutUation
of th*- power
supply
corinrrior pir
aitign*r>mti-
Ci^
P»»<*Ti ^-^_
J
—^
y »
--*
-
->— *3
^o<Q
Figure I -&-
Power ISupply Pin A^signrnf-nis
(LooWing Toward Computer)
SYSTEM
rNTERFACE
The 800XL
provides
the iollowing
interlaces:
o
Serial input/output {SIO)
o
Keyboard [nterfacc
O
Controller ilacks
o
Cartridge Intrrface
o
Parallel Bus
Interface
(PBD
SERIAL INPUT/OUTPUT
fSlO) INTERFACE
TVie Atari &OOXL communicates
with peripheral devices
via an asynchronom serial
port 09>2K
Baud rale
max,)-
Data is
transmittrd and
received
a^
eight bits ol
serial data. LSB
is
sent first
preceded by a logic
7^ro start bit and
%*icre^drd
by
a
lo(;ic one ^top bit- The serial data
out is
transruitted or
received as
positive logic
Jhc
serial data out line always
assumes its
new state when the serial
clock
out lir>c
goes high-
Ck>ck
out goes low
in the
center
ol
data out-
The bus
protocol specifies that all commands must
originate
from
tfie computer
and that peripherals present
data on the bus
only when
commanded
to do so-
Every
bus operation
goes
to completion before another biis
operation
in
initiated-
An
error
delected at any point
in
the bus operation aborts
iKc entire
sequence.
A btss
operation
consists of the
following
elements:
8D0XL
Computer
1-11
Field
Service
Manual
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