
TABLE
OF CONTENTS
LIST
OF
SECTION
SECTION
ILLUSTRATIONS
ONE--INTRODUCTION
Main
Conponents
Case
design
Differences
TWO..THEORY
Overview
Main
OF OPERATION
Systen
Microprocessing
GIue
Main
Direct
MFP Interrupt
Audio/Video
Video
Video Display
GIue
Memory Control-Ler
Sound
Video Interface
from
520l1040ST
Menory
l4enory
subsystem
Shifter
Synthesizer
unit
Access
Control
Menory
11
t.2
t.2
I.5
2.t
2.2
2.2
2.2
2.3
2.3
2.4
2.5
2.5
2.5
2.6
2.6
2.6
2.6
Mega
Service
Manua1
Input/output
MIDI
Intelligent
Parallel Interface
RS232
Disk Drive
Hard
Systen Startup
System Errors
Functional
Systen
Interface
Disk
block
clock
i.1
subsystens
Keyboard
Interface
Interface
diagran
diagra-m
Table
2.8
2.8
2.9
2.70
2.Lt
2.L2
2.L3
2.t4
2.15
2.L6
2.t7
of Contents

SECTION
THREE--TESTING
THE
MBGA
Overview
Test equipnent
Test Configuration
Trouble-Shooting
Diagnostic
ST
Power-up
RAM test
ROM
Cartridge
test
Color test
Keyboard
MIDI test
RS232 test
test
Audio test
Tining test
DMA test
Floppy
Disk test
Printer/Joystick
Monitor
Res
High
Blitter test
Codes
test
port
Quick
Clock
Expansion
Error
dead
a
test
test
Reference
unit
3.1
3.1
3.2
3.2
3.4
3.4
3.6
3.7
3.7
3.9
3.9
10
3.
11
3.
3.r7
3.r2
13
3.
3.t5
3.16
3.L6
3.L7
3.r7
3.18
SECTION
SECTION
Mega Service
FOUR--DISASSBMBLY/ASSEMBLY
FIVE-.SYMPTOM
Display
Disk
Keyboard
MIDI
R5232
Printer
Hard
Real
Blitter
Manual
CHECKLIST
problems
Drive
problens
problems
problens
Problems
Disk
Time
Problens
í.2
Problens
Problens
Clock
Problens
Table of
5.t
5.L
5.2
5.2
5.2
5.2
5.2
5.2
5.2
Contents

SECTION
SIX.-DIAGNOSTIC
FLOIlICHARTS
SECTION
SECTION
SECTION
SEVEN..PARTS
EIGHT-.SCHEMATICS
NINE--GLOSSARY
LIST AND
ASSEMBLY
AND
SILKSCREEI'I
DRAWINGS
Mega
Service
Manual
i.3
Tab1e of
Contents

LIST OF
ILLUSTRATIONS
FIG 1
FIG
FIG
FIG 4
FIG
FIG
FIG
FrG
FIG
FrG
FIG
FrG 12
FIG 13
MEGA
COMPUTER
2 BATTERY COMPARTMEI.IT
BACK PANEL
3
I,EM
SIDE
TOP
5
BOTTOM OF
6
MEGA MOUSE
7
t{oNrron
I
MIDI PORTS
9
10 MoUSE/JOY
11 PRINTER
RS232 PoRT
EXTERNAL
KEYBOARD
OF
FIG 14 EXTERNAL
PANEL
KEYBOARD
poRr
PoRTS
PORT
FLOPPY
HARD DISK
PORT
PORT
1.1
L.2
1.3
r.3
1.4
1.4
1.5
2.7
2.8
2.9
2.LO
2.tL
2.L2
2.L3
FrG 15
16
FIG
Mega Service
FLJNCTTONAL
SYSTEM
Manual
CLOCKS
BLoCK
DTAGRAM
11 List
2.16
2.r7
Illustrations
of

SECTION ONE
INTRODUCTION
The Mega
2
conputers with
are
styled as
2 negabytes
Mega
and
disk
drive,
a
of RAM,
4 have
and an internal switching
cooling fan.
Since the
size
of its RAM,
refers
to both
Power Light
Mega
and
sinilar
nain CPU
4 are Motorola
architectures
unit
with a detached
the Mega 4 contains 4 negabytes. Both the Viega
a built-in 1 Megabyte
onty difference between
nar¡ual
this
products.
will
use
MC68000 nicroprocessor based
to the
520ST/
1040ST line. They
keyboard. The Mega 2 has
(720K
'
fornatted)
power
Mega 2
the
Mega
inch floppy
3,5
supply with built-in
Mega
and
generic
as a
'
Disk
Drive
Drive Busy Light
4 is the
tern
2
which
Mega
Service
Manua1
FIG. 1
ItIEGA
COMPUTER SYSTEM
1.1
Introduction

The main
the
components
Main board assembly
o
Disk drive
o
Power supply
o
RF Shield
o
CPU
o
Keyboard assembly
o
Interface board
o
Keyboard
o
Mouse board assembly
o
Mouse Plastics
o
of
CPU
Plastic case
KEYBOARD
Plastics
MOUSE
Mega 2 and
& cooling
(upper
assembly
(upper
CASE
lower)
and
(upper
(upper
DESIGN
fan
and
and
Mega
lower)
and
lower)
4 are:
lower)
the
Mega
Figures
keyboard
Battery
Cover
size AA Batteries
Service
1
thru 4
portion,
Housing
--
Manual
CPU
shows
and figure
the
shows the
7
+
(+)(-)
FIG. 2
BATTERY COMPARTMENT
r.2
portion
of the
mouse.
IUEGA,
6
ar¡d
5
Top
of
Computer
Introduction
shows

On/Off
lo
Power
loppy
I
Js
Printer
Frc.
BACK PANEL
3
Midi
ln
Mega
Service
Cartridge
Manual 1.3
Keyboard
FIG. 4
LEFT SIDE PANEL
Introduction

Function
Keys
Calculator
Keypad
¡oyst¡Jx
I
I
Port
Computer
Jack
V
MouseiJoystick
I
Arrow
FIG.
TOP OF KEYBOARD
5
Keys
Bottom
Keyboard
of
Mega
Service
Manual
FIG.
BOTTOM OF KEYBOARD
5
1
.ll
Introduction

Clicking
Left Mouse
Button
FrG.
MEGA
7
UOUSE
Right
Button
Mouse
Differences
New version of
o
o More
o
o
o
o
o
nenory requiring
ReaI
tine
clock chip
Graphics Co-Processor
Internal expansion
Cooling
New
fan
styling with
case
T0S
fron
520ST/1040ST
74LS243
buffers on
& support circuit,
(BITtsLiT)
connector
detached
& support circuit
keyboard
MAD lines
Mega
Service
Manual
r.5 Introducti.on


SECTION
THEORY OF OPERATION
OVERVIEW
T!{O
The Mega 2 and
LSI
chip set,
ba¡rk of
one
the Mega 4.
systen
(central processing
and case styling.
2 Mega-bytes of
Ttre hardware can be considered
Mega 4 share a coruDon architecture,
Input/Output subsystens
Main
System
Mc680o0 running at SMltz
o
192 Kbyte Read Only
o
2
o
Direct Menory
o
o Systen
Interrupt control
o
Bit Mapped video display,
o
anywhere
BITBLiT
o
Monitor
o
Audio output:
o
Mega-byte
or 4
tining and
Audio/Video Subsystem
in nenory.
32O
support
x 200
x 200
x
400
a.
b. 640
c. 640
interface analog:
Ttre only difference
RAM, for a total of 4
unit ar¡d
.
Memory
Randon Access Menory
Access
programmable
support
Bus control
There
pixel,
pixel,
pixet,
16
4
nonochrone
using
are
color
color
RGB, Monochrone
sound chip
Mega-bytes of
as consisting of
support chips)
bytes of
l2k
three display
palette
palette
îron
fron
with
!12
J
using the sa.ne
is the addition
RAM
nain
a
a¡rd several
RAM, relocatable
nodes available:
jL2
selectÍons
selections
voices
of
on
Mega
Input/Output Subsystens
Intelligent
o
Parallel
o
RS-232C serial
o
Port & connector
DMA
o
Hard disk
o
Musical
o
Digital
Time Clock with
ReaI
o
Port
ROM
o
Service
ManuaL
Keyboard
printer
drive
instrunent
Interface
2
with
interface
button
(Centronics)
interface
for
external
interface &
network connunication
(MIDI).
battery
Laser
backup
2.7
mouse/ioystick interface
drive
Printer
Musical
:
Theory of Operation
Instrunent

MAIN
SYSTEM
microprocessing
The
(ROM
general
data
and
purpose
Mega uses
The
bus,
Glue
important
computer.
thè
Clock
KHz clocks.
Video
generãtlsignals
to
use¿
register
operation
Interrupt
main system
RAM)
,
DMA controller.
the
Z4 Uit
(naned
component
address
functions
The
because
dividers--
tining--
in Gtue
(done
by
B-Lank,
wfrich
the
priority--
includes
systen
MicroProcessing
Motorola
bus
that
takes
for
nay be
Operating
the
control,
MC68000
nicroprocessor,
Glue
it holds
is
it
nay be
ttre
DE
the
(Display
the
involved
sumnarÍzed
Mtlz clock
I
video
written
System).
interrupts
fron the
intepupt
Unit
16 bit
running
systen
in nearly
as
and outputs
Enable),
display.
configUre
to
MFP
codeffisofpriorityonoutputsIP11andÍPL2tothe
interrupts,
no
68000.
These
interrupt,
leve1s
HSYNC
correspond
interruPt.
to
unit,
control,
external/32
I
at
together)
every
follows:
2
Jlsync:
There
is a
for
and video
interrupts,
MFP
main
bj-t
Mflz.
is
nemory
internal
such an
operation
Mllz and
gnd Hsync
Ìead/Write
60 Hz
or
50
tining
VSYNC
and
in
500
are
are
Signa]
crrip
Genàrator,
DMA,
MFP,
Memory
It arbitrates
devices
from
IlleEal
certain
sized
the
respond within
read
DTACK.
Mega Service
conditions
to
data
processor
from
Bus
and
qlbitration--
Controller,
Menory
the
Controller,
bus
interfering
condition
violated,
are
a word sized
in user
is
required tine
the
nemory
Ma¡rual
and
Glue
DMA
,
ROMs.
and
to
during
with
detectiq4--Glue
DMA transfers
other
each
such
register,
mode.
AIso occurs
linit.
Memory
the
2.2
decodes
addresses
Controller,
receives
It
synchronize
to
(see
DMA
asserts
as
writing
writing
or
if a
For example,
Controller
Progranmable
signals
data
prevent
below)
Bus
to
to
'
Error
ROM,
system
device
the
does
Theory
generate
to
Sound
from the
transfer.
CPU and
(BERR)
writing
DeII¡ory
does
tries to
CPU
not
of
assert
Operation
DMA
if
byte
when
not

Main
Menory
Main
two
banks
sLot alrows
addressable.
menory
(2
Mega-byte
access
The
buffers, Menory
nostly
tine
bits
up
Mbytes,
giving
current
converts
All
is
determines how
Controller
RAMs,
data
in
ROM,
wíth
R.{M is
or
of a word
1 Megabit
of
organized
8 bits
at a tine.
and odd addresses
X 1
while in
two tines
BAM menory
Note:
These
The
Operating
nap:
the
are reset
versions
Menory
Controller--takes
to Row Address
RAIì|
accesses
progrannable
loads
during direct nernory
for
poner-up.
at
the Video Shifter
consists
each) of d¡manic RAM.
of L92 kbytes
to 128 Kbytes
components
of
controller,
optional
as
chips; in
the Mega
nemory,
the
segnents loaded
16
bit
Even nunbered
the Mega 2
4 there is
or 4 Mbytes.
000008-000800
000800-1FFFFF
200000-3FFFFF
first
8 bytes
vectors
which the
Systen is located
(192k).
Strobe
are controlled
up to 4
Megabytes
nuch Eernory
Ttre Memory
access
rn
ROM.
of
ne¡nory
the
a¡¡d
Glue. Tt¡e
systen
fron
words
refer
nay
and
addresses refer
to the low
there
a¡r additional
Systen nenory
low
bank
high
bank
of ROM are napped
68000 uses
in
two
addresses fron
(RAS)
by this Atari
is
and Column
nenory.
of
present
proprietary
and
Controller refreshes
with display
(DMA).
data,
of ROM
addition,
All
nenory is
are:
Operating
disk into RAM.
be
accessed 16
I bits. RAIII
are 16
chips,
bank
(priveliged
(Mega
4 only)
into
on start-up.
lMeg
x
I
the address
Address
Tt¡e
Operating
prograns
gives
and
and
the
one
or
cartridge
directly
ROM,
System resides
RAM,
bits
RAM
at a
to the high
ís made
giving
of L6
addresses
ROM
chips,
access)
O-7.
chips
in
bus and
receives
or
(CAS).
which
System
Menory
dynanic
Strobe
chip,
the
the
I
z
Glue--decodes
signals
hardware
to
registers
functions.
Direct
Kilobits/sec)
500
controllers.
hard
speed.
address
disk
For DlvlA
of
Controller
many
bytes)
data. The
Controller
transferred
Mega
Service Manual
addresses for RAM
enable these devices
provide
to
See Glue
description
Direct Menory Access
menory
access is
and
The floppy
(or
other devices on the hard
to take
provided
high
speed
disks transfer
place,
where to tal<e data
is
set up
and the
(which
channel,
peripheral
entire block of data
and
to or
peripheral
the
from menory
without intervention
a¡rd ROM
(also
decodes
chip selects,
above.
).
to
(up
support both low
to 8
data via low
disk
Menory
the
fron
given
is
(the
before the
2.3
put
or
high
speed or low
a
comnand to send
must
size
operation
a¡rd asserts
addresses for
as well as nany
speed
Megabits/sec)
port)
speed
transfer
Controller
data
in
Sbit device
DMA
given
is
RAM,
speed, and how
or
given
be
to
starts)
by the CPU.
Theory
of Operation
output
nost
other
(25O
to
and the
at high
the
DMA
the
receive
DMA
the
is
then

exanple,
For
floppy
the
ready
Ci".l
will
which
next
Itr"
nenory
requesting
is
assert
reaa.
This
to
lost
by
Glüe
read
was
byte
äpecified
to
high
At
ready
to
ACK
The
,r."."".ry
is
transfer
slowing
or
conúro1ler
asserti"á
signal
will
byte
the
set
fron
fJ-oppy
data
previously.
up
thè
number
are
on
speed
transfer
tel
to
Controller
DMA
ä.roty.
to
down
in a
will
ponO,
the
fron
floppy
ôr
sinilár.
FDRQ.
(hard
to
peripheral
tne
if the
the
transfer
signal
óue chip
tn"
Menory
Óontrotler
DMA
the
The
controller,
uyt"s
disk
or
can
68000
Data
tra¡¡sfer
has
The
port),
fron
store
is using
nay
sector
a
of
the
DItlA,
will
Controller,
Controller
DMA
and
been
floppy
there
DMA chip,
the
know
up
be
speed'
the
to
the
input
the
fron
Controller
the
read
the
-and
a¡rd
place
it
will
process
the
transferred'
initiates
a
is
the
ís
byte
bytes
l2
bus,
fron
every
difference:
DMA
avaÍlable
in
and
port
the
in
the
wait
repeat
to
a
ar¡d
Controller
floppy
that
byte
Menory
then
wítl
Tra¡rsfers
transfer
as
Controller
or
internal
nust
DMA
the
without
nenory'
byte
is
signal
address
for the
until
from
by
byte
a
will
has been
De¡rory'
wait
being
68901
The
used.
are
MFp.
ñ;
receives
MFp
if the
ready
Iow)
assert
will
Th;8
interrupt
respond,
to
GIue
and
DTACK
read
The
derecr
HDINT),
(MONOMOÑI-,--R5232
parallef'óort
iine),'S'giO
ñoi árr
while
MFp
timers,
RS232
used
port
handles
MFP
interrupt
Each
inputs
inlerrupt
an
is enatled,-MFPlyf
it
*nilI
put
and
lo
use
and
interrupts
ior
IRQs
operations
l/O
waitini
tñe
by
transnit
for
MFP
up
can
also
äre
input,
signals
."""tt
calculate
keyboard
for
Operating
r¡cr
vector
a
controlted
(including
gÚSV,
operation
an
and
InterruPt
16
to
nasked
be
directly
or
interrupt
(interrupt
number
address
the
by
display
MIDI
and
interrupts.
use
System
receive
Control
interrupts.
or
off
readable
generates
driven
be
witt
acknowledge
acknowledge).
data
the
on
the
CTS,
enable
data,
conplete.
to
for
clocks'
of
MFP
999,
(DE,
event
the
are:
and
The
Currently
disabled
the
by
interrupt
an
low.
(Fco-2ìigh and
bus,
interrupt
nonochrone
RI),
equals
MFP timers.
CPU can
The
tining
all
by
CPU.
When
The
which
disk
start
also
MFP
used
and
one
but
progrernning
the
When
internally,
is
CPU
the
vltlA
will
MFP
cPU
the
routine'
monitor
(FDINT
of
poll
has
a¡rd
display
the
four
the
by
Mega
Service
ltlanual
2.4
Theory
OPeration
of

The
Menory
graphics
video
Generator
controller,
output.
AUDIO/VIDEO
video
processing
subsysten
Glue,
unit
The audio
consists
graphics
a
(BImLiT)
subsysten
chip with a transistor
SUBSYSTEM
of
the video display nenory,
control chip
and a discrete
,
consists
output
anplifier.
of
(video
section
Progra.mnable
a
shifter),
to drive
the
a
the
Sound
There
nay
be used in
only
is
Ievels
112
is
one
used
for inverse/nornal
of intensity
colors
taken fron
logical
shifter
palette;
either
the
network
monochrome
separate
origin
Display
plane (see
will
note
on or off. Thus,
power
lrd
to
output.
Display
located
Eenory
resolution)
nemory
half
to forn
page
boundary. The
the Menory
Systen
or
infornation
Shifter
wirl
strean. rn
color,
of red,
bits
green,
Video
are 16
used in high resorution
color
row resorution,
palette
Shifter
registers
nay
4
video). Each
possible.
the
output the red,
there are three
proportion
node,
nemory
For
palette
description
$. The
=
the
is
of red,
blue,
given
a
referred
and
pixel,
to by
of
video
green,
outputs for
the nu¡nber
three
the voltage level
color
Video Display
part
outputs
palettes
of nain nenory
at the top left
is
configured as 1, 2,
one
planes
Kilobyte
32
interwoven
physical
Iogical
starting address of display
Controller's
Video
Base
Address
application. The Menory
into
the video
decode this infornation
nonochrone
are conbined fron
and blue.
Shifter 16
mode,
each bit represents
each
plane
Ín
be used
(actuarly,
palette
green,
the coror
getting
dispray menory
and
blue
each color. Each
possible
of
are sr¡nmed
give
to
are bypassed
Menory
with
corner
or
by 16 bit
plane
register
Controller
uits
at a tine,
generate
to
generate
to
the shifter.
in
high
onry bit
so
resolution,
progr¡mmed
is
there
which is
infornation
levers
specified
output levels
through
I equal
a¡rd there is
physical
the
of the
(nigh,
4
words into
nediun,
starting
Eer¡ory is
by
will load
and the Video
a seriar
pixer
1
the comect level
0
of
AII 16
register
are
a¡¡d
for
are 8 x
I x I
displayed
from
betow). The
by
each
that
is
output is
is
Z to
a resistor
steps. In
screen
screen.
1ow
or
contiguous
at a 256 byte
placed
in
the Operating
display
dispray
on or off. rn
0
8
=
a
For
exanple, in
the
Video Shifter for
Video
nunber
nunber
those revers,
from
Mega
Shifter
(0-15),
(e.s.
palette
the
Service ManuaÌ 2.5
conbines
and takes the
0101=5,
then takes
low resolution
each
use color from
referenced
(16
word
pixels
bit 0 from
color
bit
by those four
from
1 fron
(4
ptanes)
displayed
each word
the
palette
palette
plane
each
bits,
4 words
on the
to forn
referenced
register
and outputs
etc.
Theory
loaded
are
screen. Tt¡e
a four
a¡rd
!)
the coror
of Operation
into
bit
by that
outputs

G1ue
GIue
output,
causes
the
the
scanned
off
scan
go
the
sigPal.
and
the
address
Memory
anâ
the
not
is
the
to
nonitor
In addition
output
display
active-only
control
nenory
The
synthesis,
"¡.
"ii"t
Hz to
which
tZJ
are
provides
monitor/RF output.
starting
counter
Controller
data
video
in a
monitor
or
tining
address
during
a¡¡d
shoutd
output
be
fron the
dilplayable
output
T.V.
to
signals
vertical
inputs
the
associated
lñto tne
changing
when
yM2149
sound
The clock
KHz,
míxed and
Progranmable
effects,
input
There are
sent
control
the
of
vertical
Video
loaded
Video
part
RF
a¡rd
Menory
from
Video
the color
ís
to the
Shifter.
Sound
Sound
and audio
2 MHz; the
three
nonitor
the
to
VSYNC
input
display
blanking.
ShÍfter
into
that
the
Vídeo
Shifter
screen.
the
of
modulator.
horizontal
a¡rd
Controller
nentioned
Glue
video.
with
CMPCS
attributes
SYnthesizer
Generator
feedback
frequency
sound
channels
speaker.
Menory
the
to
nenory
DISPLAY
a display
Shifter.
during
VSYNC
These
sweep
DCYC
(color
in
the
(PSG)
(e.g.
output
Controller,
Menory
to be
reloaded
EI{ABLE
line
periods
and
signals
to
above,
there
strobes
nap select)
color
produces
alarns
response
fron
video
Controller
into
(DE)
tells
ís being
BLANK shuts
when
HSYNC
synchronize
the
the
both
display
are two
data
from
is
palettes.
nusic
key
a¡rd
the
is
chip,
range
30
pSG
The
relating to
This
Iocation
Single
transfer
associated
addition,
registers,
filling,
seãd
transformations,
For
included
Service
Mega
printer
a
r.s
a destination
to
multiple
or
to destination.
with
with
the
more infornation,
in the
Manual
is also
used
port,
DMA device
word
merging
the
16 wõrd
the
blit can
pattern
etc.
Developer
also
filling,
in
disk
Atari
that
location
increments
There are
system
the
drive,
Blitter
moves
source
of
block
through
and
16
patterns ran a¡rd
used to
be
brush
please
refer
Kit.
2.6
various
for
RS232.
and
nenory
of
given
a
decrenents
possible logic operation
destination
a¡rd
three
perforn
line
to
operations
drawing,
user
the
f/O
fron a source
data
logic
provided
are
L6 bit
such
and
text
nanual
Theory of
functions
operation.
for
rules
data.
end-nask
as area
graphic
which
Operation
In
is

Real
Tine
Clock
Ttris
device has
data
Iines
signal lines
RESET
The
will
the CLKOIJII
JV
down.
are expressed with BCD
are
used to
RTCCS, RTCRD, RTCh¡R
line is
naín clock supplied to
also
be adjusted by a trimmer condenser
line
battery backup ca¡¡ be used
counters for
program
provided
a standard
the device
to reset
the devÍce is
clock signal
Battery Backup
with
Time
and Calendar
code. The
and access
which
the chip when
keep
to
buÍIt-in. Clock
lower four
address
the clock
generated
a
32.768
so that it
16.384 Xfrz.
of
the clock running
fron
a decoder. A
the system is reset.
l<hz
oscillator
will output
In
and data
through
which
through
addition, a
during
power
For nore
nanufacturer
detail,
(RICOH
please
part
number RP5C15)
refer
to
the application na¡rual
fron
the
Mega
Service Manual 2.7
Theory
of Operation

The
RGB a¡rd
MONOMQN
the
Iow).
The
types
th¡o
nonochrone.
input
possible
interface
of
presence
The
(when
â
disPlays
Video
Interface
are
of
nonochrone
are:
provided in the
nonochrone
a
nonitor
nonitor
is connected,
Megas
ís detected
are
it
a¡alog
will
by
be
Monochrome:
the
of
resistor
RGB:
colors
output.
Monitor
Inputs:
û
single
Video
network
each
enitter
Shifter.
sums
have an
Hsync--TTL
Vsync--TIL
level,
Ievel,
Monochrone--digital
R,G,B--analog
Audio
-
ComPosite
-
General
-
Monochrome
-
Audio
-
Green
-
Plus
-
Horizontal
-
P-P,
12-Voll
Audio--1V.
Monitor
1
2
3
4
5
6
7-Red
I
9
foltower
outputs
emitter
negative,
negative,
0-1.OV
1k ohn.
Out
SYnc
PurPose
Detedt
ln
Pullup
SYnc
a.nplifier
for each
follower
P-P'
1.0V
P-P'
75
OutPut
driving
color.
a.mplifier
k ohn.
3.3
k ohn.
3.3
ohn.
J!
ohn.
10 - Blue
11
Monochrome
-
12
Vertical
-
13
Ground
-
Ttre
Sync
the output
three
drive
to
Mega Service
Manual
FIG.
MONITOR
2.8
8
PORT
Theory
Operation
of

rNPUT/oUTPUT
SUBSYSTEMS
Musical
The
integration
other
and
Kilobaud)
ptog"an ilfornation
"rrd
(MIDI
thar
by
oUT
data
one
of
devices
as¡rnchronous
also
co.rsi"f'ãi
bit.
stoP
Connunication
to
in
l[ã-OóiO
MFP
the
via
chip
inverters
two
order
writeJ-to
6850
outside
transistor
through
THRU
Musical
Instrunent
Mega
the
supports
takes
in
interrupt
inverters
trdo
the
on
allow
to
Instrument
nusiõ
with
fossessing
current
provided
is
optionat
the
bits
A.t.
8
place
response
controller.
on
the
side.
output
input
to
chaining
Connunication
Digital
Interface
sysnthesizers'
MIDI
loop
interfaces.
serial
two
by
ttlt¡t
preceded by
6850
a
via
interrupts
to
the
of
Ttre
tra¡rsnit
The
connector
nultiple
(MIDI)
sequencers'
communication
ports, MIDI
ntnu
port)
one
nCfe.
which
systen
start
The
are
is
side
input
signal
where
devices
allows
HiSh
speed
of
gUT
MIDI
.
a¡rd
bit
CPU
passed
interfaced
an
a¡rd
is routed
is called
it
on the
MIDI
drun boxes
(3L'25
keyboard
MIDI
and
specifies
followed
reads
fron
to the
LED/photo-
around
bus'
the
IN
and
the
II{IDI
Mega
Service
Js
J¡
Manual
Midi
1
-
2
-
3
-
4
-
5
-
Midi
1
-
2
-
3
-
4
-
5
-
Out
Transmit
THRU
Ground
Shield
LooP
THRU
Transmit
OUT
OUT
ln
Not
Not
Not Connected
lN
lN
LooP
Connected
Connected
Receive
Return
LooP
FIG.
MIDI
2.9
Return
PORTS
Data
Return
Data
Data
9
Theory
OPer'ttion
of

Intelligent Keyboard
keyboard
The
nouse data,
of-day data
requests by the
6850 device
Microconputer Unit.
ROM are self-test diagnostics which are
whenever the
by the CPU.
interrupts
The 2 Button Mouse is
joystick
(year,
The MC6850 is read
which are
trarismits
data,
month, day,
CPU. Comnunication is
a¡rd
RESET
the keyboard assenbly by the
on
The HD6301 has internal RAM
connand
passed
characteristics: a resolution of
10 inches/second
joystick/nouse
Ieft
button.
button
four
directions
is
The right
wired to the second
and a
port
(up,
has inputs
button
down, etc. ) and
v
nake/break
key scan codes,
in response
hour, minute,
controlled
is
sent over
a¡¡d written to
to
a¡r opto-mechanical
naxinum
Mouse/Joystick
1
-
2
-
3 - Left/YA
4 - Right/YB
5
-
6
-
7-
I
-
9
-
CPU by Èhe
the
100
counts/inch,
pulse phase
for
up, down,
equals the
joystick
Up/XB
Down/XA
Not
Fire/Left
+sVDC
Ground
Joyl
port
one trigger.
Connected
Bulton
Fire/Right
to external
the serial connunication
joystick
Bulton
ASCII
events, and
second)
on the
lMHz
and
perforned
by the CPU in response to
MFP interrupt
device with the
a
error of
in response
nain
board by
8 bit
RoM. Included in
poh'er-up
at
controller.
following
mæ<imun
velocity of
percent.
50
left, ríght, right
trigger, a.nd the
joystick
trigger.
The
3
codes,
tine-
to
a
HD6301
and
line
The
button,
left
has
Mega
Service Manual
Joystick
1-up
2
Down
-
3 - Lefl
4
Right
-
Reserved
5
-
Fire
6
-
7-
+SVDC
8
Ground
-
Not
9
-
FIG.
MOusE/JoY
Button
Connected
10
PoRT
2.ro
Theory
Operation
of

Parallel
Interface
parallel
The
printer
centronics
Data
Centronics
on
ohn resistor
read
chip
interface,
STROBE
and strobe
printers
the data lines
port
Ttre
directly
select.
port
but
BUSY
and
signals
are compatible
should
pull-up
can
on the
programned
be
by the CPU,
prinarily
is
can also
are
supported. BUSY
are output
not
exceed 2.3 mA.
printer
to
with
intended
be used as a
by the YM2149
with
this
(TtrÍs
side.
)
input
be
Gtue
doing
or output.
address
as
general
is read
port.
a Centronics
purpose
by the MFp
psc
chíp.
The
current
corresponds
The
PSG
decode
to
r/0
Not
loading
to
a
chip
provide
type
port.
chip.
all
2.2k
is
Mega
Service Manual
Printer
1
STROBE
ç
-
2-Dala0
Output
3-Data1
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2f
16
rr 16
!5
19
4-Dala2
5-Data3
10
Not
6-Data4
7-Data5
8-Dala6
9-Dala7
11
12-17
18-25
-
-
Connected
BUSY
Not
-
Ground
-
lnput
Connected
FIG. 11
PRINTER PORT
2.17
Theory
of Operation

RS232C Interface
RS232C
The
handshake control
five
with
Ready are
and
(Universal
data
output
Detect are
Ring
Synchronous/Asynchronous
transmission
divided by the
clock
second
+/-
for receiver
supported.
are
I2v. supply
interface
by the
input to the
and
tiner
D
and
meet the
provides
signals:
PSG chip;
asynchronous
Reguest to
Clear to
chip.
MFP
Receiver/Tra¡rsnitter)
reception.
(pin
16) output
transnitter.
The
Data
f488 tine drivers
EIA
RS232C
standard
Send,
2.4576
the
of
rate of
and
serial
a¡rd
Send
Carrier
Data
contains
MFP
The
MHz clock
to
MFP
50
1489
to
provide
19200
to
line receivers
for electrical
connt¡¡¡ication
Terninal
Data
Detect,
USART
a
the
the
handles
MFP
bits
is
basic
per
which
with
interface.
\
Mega Service
Manuaf
Modem
1
Protective
-
Transmitted
2
-
Received Data
3
-
4
Requesl
-
5 - Clear
Not Connected
6
-
7 - Signal
Data
8
-
9-19
-
Ground
Data
to
Send
lo Send
Ground
RePeat
Carrier
Not Connected
FIG.
RS232
2.L2
T2
PoRT
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20
-
21
-
22
-
23-25
Terminal Ready
Data
Not Connected
Ring lndicator
Not
-
Theory of
'¡
2t
Connected
Operation

Disk Drive
Interface
The Mega
lrJestern
Digital
conputers
L772) and
have
a
logic for
built-in floppy
selecting
double sided drives. The Mega has one built-in
provision
Controller
outputs
through
Iine, via
comnands, such as
passes
and
Systen,
CPU
when the operation
overhead of disk I/0.
for
one external disk drive. The hlestern Digital WDt772
services both drives. Drive
on the
the
above,
YM2149 PSG
DMA
Controller,
MFP interrupt
the
seek,
data to the
for
details
chip. The CPU reads
Tl:e 1772
controller. Tl:re L772
fornat
DMA Controller
is
conplete.
track,
on DMA
and side selection
Ínterrupts
write
(see
DMA
tra¡rsfer).
The
CPU
is
disk controller
up to
floppy disk
a¡rd writes
the CPU on
sector,
trr¡o single
accepts
read
drive a¡rd
is
done
to the
the
high
sector,
controller under
The L772 ínbemupts the
freed fron
nuch
of the
(a
or
by
L772
INTR
level
etc.
Main
Mega
Service Manual
I
Floppy
2-Side0Select
3
4 - lndex
5-Drive0Select
6-DrivelSelect
7 - Logic
I
9 - Direction
10
tlsk
1 - Read Dala
Logic Ground
-
-
-
Motor
Step
Pulse
Ground
On
FrG.
EXTERNAL
FLOPPY
2.13 Theory of Operation
11
Write Data
-
12
Write
Track
Write
Gale
00
Protecl
ln
L3
PORT
13
14
-
-
-

hard
The
controller;
is sent
board
a¡rd
Interface)
l,Jriting
to
external
accept
DMA chip
acknowledge
Memory
to
go
low and
data,
Cóntroller
device.
Controller.
DMA
disk
the
command
drive
hard
conna¡¡ds
paraneter
the externâI
to
CAl
fJhen
HDRQ will
that
respond
is on the
data
nust
feeds
Transfers
can
Port;
Hard
interface
disk
via an
block.
controller
go
high.
is available,
data
driven
be
within
data
place
take
Interface
Disk
is
controller
SCSI-like
Data
causes
DMA tra¡¡sfers
high by
2!0
or
bus
to
HDCS
the
nanoseconds
been
has
or accepts
to
up
at
provided through
is off-board
(SnaII
is transferred
(Hard
are
the
or
external
1 Mbyte/second.
Conputer
Disk
controlled
device
controller.
with
fron the bus-
read
data
via
Chip
is
ACK
fron the
DMA
the
and is
System
DMA.
Se]ect)
the
by
ready to
(}ow)
The
to
The
DMA
Mega
Service
a
Manual
Disk
Had
1-Data0
2-Dala1
3-Data2
4-Data3
5-Data4
6-Data5
7-Data6
8-Data7
Chip
9
-
lnterruPt
10
-
11 - Ground
Reset
1
2
-
EXTERNAL
Select
Request
FIG. 14
HARD DISK
2.r4
PORT
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13
Ground
-
Acknowledge
14
-
'15
Ground
-
A1
16
-
17
Ground
-
18
Read/Write
-
19
Data
-
Theory of
Request
Operation

SYSTEM
STARTUP
After
a
executÍng at
(GIue
000004
FEFFFF).
maps
8 bytes of ROM
points
The following
1. Perforn
2. Read
is a
cartridge tal<es over here). If not,
Check for
3.
written), initialÍze
running
it
was a warm start.
Initialize
4.
Initialize
5.
If not
6.
Set up operating system variables in RAM.
7.
8.
Set up exception
RESET
the address
to the start
the
"nagic
(power-up
pointed
FC0000-J
at
of the operating
sequence is
reset instruction
a
longword
at cartridge
nunber",
or reset
execute fron
a warn start
the nenory
the application which
PSG
the
color
h,arn start, zero De[¡ory.
a
chip, deselect
palettes
vectors.
button) the
to by
then executed:
locations
into
the addresses
(outputs
address
systen code in ROM
the cartridge
continue.
(see
if RAM locations
running
was
disk drives.
a¡rd set screen
68000 will
4-J, which is RoM
reset
a
F40000. If
controller,
pulse).
before
address.
0-7).
vrere
Location
(FCOOOO-
the
data
(diagnostic
previ.ously
and continue
the reset if
start
read
Initialize MFP.
9.
10.
Set screen
11. Attempt
progran
The 68000 has a feature calted
place
when the CPU detects an emor
instrtrctions
vector
routine
the
occurrences
general purpose
on
operating
exception
Mega
when an Ínterrupt or bus error is indicated
are executed.
(address
pointed
operating system.
(interrupts
the screen
systen).
which occurred.
Service
ManuaL 2.15 Theory
resolutÍon.
to boot
if
succeeded.
to a
to by
floppy;
SYSTEM
An exception
routine)
the vector. E:<ception vectors
Those exceptions whích
being legitimate) have
routine which wiII
(nushroon
clouds in
The number of
attenpt to boot
ERRORS
exception
internally,
wiII cause the CPU to fetch a
fron
RAM
and start
display some
older versions of disk loaded
bonbs equals the
hard
processing,
by external
when certain
or
processing
are
not have legitimate
do
vectors
nunber
which takes
initialized
pointing
of bonbs
nunber
of Operation
disk;
logic,
types of
at the
to a
showing
of the
run
or
by

nay or ¡nay
files
System
from disk wiII cause the
errors
Verify the diskette and
computer.
not
be
system to crash,
drive before
disk
recoverable.
necessitating
attempting
Errors
to repair
in
loading
reset.
a
the
NUMBER OF BOMBS
(No.
26,28,30, ana 64-79 wiII
2 Bus
]
Error.
Address Error. Processor attenpted
AND MEANINGS
Glue asserted bus error
sized data on an odd
IIIegaI
or
Zero
5
Chk
6
this,
Trapv
7
Privilege Víolation. CPU
B
location in
Trace. If
9
execute
sofuware.
Instruction.
RAM which nas not a
Divide. Processor was asked
Instruction. This is a
it nust
install
Instruction.
supervisor
trace
bit
this exception after every
10 Line 1010 Ernulator.
Provided to allow user to
11 Line 1111 Emu1ator. See
12-23 Unassigned, shouLd
24
Spurious
25-3L Autovector
should
32-63
TRAP
ion
64-lg MFP
BO-255 User
Interrupt.
Interrupt.
no
have
Instruction.
processing.
interrupts.
interrupts.
occurrence.
not bomb, as
address.
Processor fetched an
legal instruction.
to
legal instruction,
handler.
a
instruction.
Chk
See
was in user
address space.
is
be
Bus
The CPU read
in
set
CPU read
the
pattern
emulate
Line 1010
no
occurrence.
error
Even nunbered
during
instruction
they are
CPU detected an error.
or
to access word or
legitinate.
long word
instruction from
perforn
mode, tried to
status
division by zeto.
a
if
software uses
access
register, the CPU will
instruction. Used to debug
1010 as an
his own
Emulator.
instructions.
interrupt
vectors are used, others
which forced except-
instruction.
processing.
)
ROM
a
Note: If
Mega
Service
you
have an emor
possible
1- The
2- The
the 4O-folder
can be used to
No ha¡rdles left or
3-
Manual
errors are:
file in
total
number of
bad.
as
"T0S
in
the sysLem
nessage such
progress
is
folders
linit. However, there
extend this
too
2.L6
limitation on
nany
open
ERROR
is
a
then the
35",
has
exceeded
program
folders.
files.
Theory of Operation
which

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SECÎION
TESTING
OVERVIEI{¡
THREE
Ttris
software,
repair
used if
when
below.
Since
it
shouldn't
problens
give
down
troubleshooting
68000
consideration;
little
component
sub-assembly. Many
naybe
section
and test
Mega/ST
the
possible.
running
a
systematic
problen
a
processor
the cartridge,
level
the
be expected
pinpoint
or
due
tine can be
level
socketed,
naking
conputer
The following
computer:
i
Atari
i
Atari
r
Atari
I
Mega/ST
I
Mega
*
RS232
t
MIDI Loop-Back
ì
Mega/ST
t
Diskettes
I
RS232
pertains
procedures
computers.
If
the unit
of
to the test
used to verify
Tt¡e
diagnostic cartridge
gives
see
conplexity
that this docunent
the causes; rather,
approach which
to Íts nost
systems
nay
be helpful. Economics
to the
low
justified
of
it
the
may be
¡nore
when
a
likely
cost
in
expensive
verification
TEST EQUIPMEI.¡T
equipnent will
SCl224 RGB Monitor
SM124
SF354 or
Expansion Test
Loop-Back
ternirral
Monochrone
SF314
Floppy Disk
Port Test Fixture
Fixture
Connector
Cable
Test
Diagnostic
(2)
(or
Mega in
equipment, diagnostic
correct operation and
no
rrTroubleshooting
in
display
the Mega/ST
can
or
systen is
cover all
the intent
technician
can use to narrolt
source. Experience
is
assumed. Knowledge
witl
be arì ínportant
of the
troubleshooting
cheaper to
and
be needed
Monitor
Cartridge
Mega/ST
(and
critical) cotrponents
replacenent
to test the Mega/ST
(or
sinilar)
(or
Drive
(Mega
tff52
enulator node)
conputer line,
exchange the
siniJ-ar)
only)
(Revision
should be
R5232
a Dead
possible
here is
of the
down
faster.
to the
4.0)
output
Unit'r
high,
to
in
entire
troubleshoot
Mega
Service Manual
In
addition,
the following
repair
and
r
0scilloscope
*
Digital Multimeter,
*
Snall
*
Spare Parts
Ha¡rd
failed
(100MHz
Tool,
itens
computers:
Recconmended)
1l
FS
& Soldering
3.1
(or
will
better)
lron
be necessary
Testing
to

TEST CONFIGI.JRATION
With the
(IMPORTAI.IT--if
BE SURE
Connect
port,
plugged
cornputer
and
nonitor
few seconds the
skip
THE
cables
and
in so that,
MIDI
into the
Power on the
down to
next section
power
CARTRIDGE
joystick
ports,
loopback
"
"Troubleshooting
If the unit
it should
diagnostic;
and will send
diagnostic.
be disconnected
otherwise,
nessages which
In the event
pclwered
determining
taken,
compu+,er
no display
a¡¡d
the
such as
to verify
is working.
switch
cartridge
the
INSTALLED
IS
fron test
/
fixture
nouse
if the
cables
the
connectors
nonitor
output
unit. Some
nenu screen
Mega/ST
Diagnostic
is being used
the
TROIJBLESHOOTING
the
that
appears,
problen.
checking
the
This assr¡nes
the
unit
does
Ínstall
not
off,
into the
ports.
fixture
would
into their
(a
tests
should
Cartridge
Dead Unitrr.
a
a terninal
as
fron the
nay think
host
will act
A
systen
this
LED in the
powered
is
Diagnostic
have
WITH
The
ioystick
ports
not be
the
plastic
the
THE CHIPS
hard
disk
directly
were
crossed.
ports.
nonochro¡ne can
run autonatícally;
be
will
If
below.
",
the
appear.
for a
host before using
soneone
keystrokes
like
DEAD UNIÎ
is correctly
is the
elementary
and
procedure
forward
naking sure
left corner
Cartridge
enclosure,
FACINC
port,
cables
parallel
should
facing the
PIug the
PIug
the
be used
screen appeArs,
instead)
not, read
If
host computer,
is logging
input to the
configured
use
to
steps
have
the
nonitor
DOIW)
R5232
color
in
the
oD,
and
for
been
the
of
.
be
a
1. Connect a
test
emulator
cable
(IJ.U.T.
should connect
(serial
(sround)
bits of data,
for
the
Insert the
the unit.
display of
computer.
iroubleshoot.
for information on
If no activity
(2)
with
Mega
Service
dumb terninal
You can
).
program--see
in) of the
pin
to
1 stop bit,
VT)2 enulator).
If
the terninal,
The terminal
7.
Diagnostic
Diagnostic
the
If not, the
Refer
using
is
page.
next
Manual
to
use an
owner's
the
pin
(serial
2
terminal,
parity
no
Cartridge
use
conputer
to
the cartrÍdge.
on
seen
3.2
RS232
the
Mega/ST
nanual
running the
for
out)
vice versa.
a¡rd
should
be set up
(this
into the U.U.T.,
Cartridge
diagnostic
the
have to be
will
"Diagnostic
the
RS232
port
port
setting
the unit
of
l/T52
up
of the U.U.T
Connect
for
is
the
messages
9600
default
8¡¡d
appear
to troubleshoot
disassenbled
Cartridge"
display,
or
under
terminal
tÆ52.
pi.n
to
pin
bps,
condition
power
on
below
continue
Testing
The
3
7
I
on
the
tire
to

2. Disassenble
exposed
a¡¡
Replace oscillator if necessary.
68000 CPU.
not,
(2)
on
observing
(see
oscilloscope,
the CPU
doubte bus error,
input
pín
should be
conponent is malfunctioning
the conputer
Section 4,
verify
It
should be a
is halted. The
of the tn¡o
22
high
inverters
of the CPU
always.
so that the
Disassenbly).
the SMHz clock
TIL
high. If so,
reasons may
bad CPU.
3)
(BERR)
If
there
a¡¡d
on
Tt¡en check
the
as the unÍt
Glue is
printed
Power up the conputer.
the
to
pin
go
(1)
be:
Check
are
(1)
HALT line. Check
logic low
generating
Verify the clocks to GIue a¡rd Menory Controller
conponents
is
unable
responding
to verify then
read ROM or there is a
to
read or write
to a
or DMA Controller. The
The DMA
way
chip should
to check
possÍbilities,
second)
a
strongly
respond
(3)
other
although a
indicates
(if
socketed).
the CPU,
by
MFP
should respond to
FCS
to
than by elinination
hot CPU
a bad
by asserting RDY. There is
(too
hot
CPIJ.
If
still failing,
conponent wlr-leh is not
probably
an
to touch for nore
circuiÈ board is
Using
(pin
68000
bV observing signal
is
CPU
(HALT)
17
on ro
reset
bad
powered
I
pulses,
15).
of the
below. If
circuit,
(2)
on. It
some
by
the error.
replace
and
the
MFPCS
with DTACK.
of the other
the CPU
MFP
these
68901
no
two
than
If
3.
f'ron ROM
be toggling.
the CPU
(cartridge,
possibility
Verify the output of the
unit with
through the 1488 driver.
RS232.
connection
the cartridge
If
Verify also the output
nonitor,
for R,
will be
check
does
output
check the outputs to the sunnirrg
G, a¡¡d
possible.
input
the
not
read a low on this signal on
on the Video Shifter.
If
the
is unreadable,
is not halted, it
if installed)
(If
not, replace CPU. ) At this
that both
looks
all
to the
B. Note
the video
good,
terninai.
that
If using nonochrone,
to the
Video Shifter
there
is
should be reading instructions
and data a¡¡d address lines will
RS232
and
MFP
installed. If
Note
there nay be sonething
of the
(pin
chip
data
+
that
a¡rd
Video Shifter.
if BLANK is not
check output
power-up,
MFP,
pin
29, M0N0M0N. Note
is outputti.ng a signal, but
probably
problen
a
cartridge should be used to diagnose this
terminal
as a
display
device.
point,
subsystems are failing.
8)
while
is
being sent. trace it
12v. is required for
-
resistors
going
Ít will
there
powering
wrong with the
If
(if
high, no
pin
that
on the
using an RGB
external)
picture
30.
if
the CPU
cause
picture
the
with screen RArY. The
problen,
with
the
is
AIso
RS232
the
RGB
Mega
Service Manual
3.3
Testing

MEGA/ST
DIAGNOSTIC CARTRIDGE
The
diagnostic cartridge
conponent failures
several
earlier
revisions;
versions
Guide. This section
in
the conputers
this docunent
should
refer to the appropriate
gives
a brief
of each test, error codes
recommendations
The
particular,
appear,
before the
background in nonochrone)
diagnostic
the
a¡rd the screen will appear scrambled
menu is
testing, with a
Kbytes of RAIü is tested on
error wiII be
RAM is failing,
execution will
progra¡n
The
screen will be displayed
If
connect
will continue to test
keyboard fails, it will
the
terninal to the
a
for keystrokes fron
repaír.
on
program perforns
nessage
"Testing
printed.
message indicating
printed
fail
to the
screen nay not be
Lhe
because there
(the
R5232
RS232
the
Power-up
The screen will
if
a¡r emor occurs
power-up;
R5232
screen
port.
device.
is used to detect a¡rd isolate
(52O/LO4O
refers to
guide
pass/fail
or
several tests on
MFP, GIue tining,
the
if
device.
is no
stack
RAM and
¡nay turn
inactivated. The
be
The
and Mega). There
revision
4.0. Users of
Troubleshooting
are
to use with a description
criteria, and
power-up.
In
Video will
for a few
turn
in
red
the
seconds
(dark
initial
failure. The lowest
locatíon fails,
a
It is
assumed that
readable
or
print
system variables.
emors, but
red).
diagnostic
a¡¡d
Repair RAM.
user nust
progra¡n
the
if
program
no
looks
2
If
the display
used.
screen.
test title and
anount of
menu
corresponding to those tests, and then the
All nessages
The normaL
revision nunber
RAM
and
below that.
is
unreadable,
printed
are
Test Menu
screen will be dark blue
keyboard
To
controller
select tests, the user types the
to the
are displayed at the
iterations of the test or tests chosen ca¡r be
nunber
of cycles
cause the test sequence to
before
sone tests before
total
Mega
Service
completion,
numbers of cycles will be
Manual
just
before typing RETURN. Typing a zeto will
run continuously. To
hit the
the
test
escape
stops). As
3.4
key
RS232
the
R5232
terminal should be
port
as
weII
as the
with white letters. The
top,
with the
revision below, and a test
keys
return key. Many
run
by typing
in
stop a cycle
(there
each cycle conpletes, the
displayed
nay
be sone delay
on the screen.
Testing
the
in

MENU
MAIN
Mega
nnu
4u
RAI{
R
Keyboard
K
Audio
A
Fioppy
F
Graphics
G
ReaI-tine
L
Expansion
X
Run
0
iun
z
ST
and
o
Keyboard
Test
Oisk
chiP
clock
connector
Tests
AII
rnternal
Field
1987,
0
M
T
P
(Blitter)
tests
Service
Atari
Diagnostic
CorPoration--
revisioi-V----6O
ROltls
0'S'
MIDI
Timing
Printer/JoY
(R,o'c'K'A'T'L'G)
Ports
n"
Test
0S
c
S
D
H
Rev'
Version
CoIor
Serial
Port
DMA
resolution
High
4'0
Port
2
USA
NTSO
Exanine/ModifY
E
B
V
?
Enter
RS2l2
Set
iãÀgr"
Help
letter(s),
Pressing
decreases
Pressing
cartridge
After
status
space
arrA
bar
If
before
the
either
will
rhe
completion
current
continuini
be
"
keysr"oL"
nenory
rate
iia"o
outPut--5o/6o
and
up
the
it.
or
'?'
functions.
test
a
er"ãr-".po"t,
return
to
nultiple
tests
test,
"or,"id"iabte
i"-ããlãðt"0.
REIURN
the
or
to
series
the
increases
HELP
arrovJ
are
pres"ins-ihã
by
sequen"å
the
returning
or
delay
Hz
ons
e.
tion
quires disassemblY)
ishted,
hrough
seleðtion
tests.
or
e
brings
key
tests
of
any,
if
nenu'
selected'
"iff
to
Uãfore
iup-lã
i
will
These
requires
hardware
baud
pressing
it'
conpletes'
will
the
tey.
BéC
hali,
nenu'
the
the
minutes
highlighted
be
should
the
test
the
tests
the
all
sequences
Selection
registers'
the
on
rate
brief
a
up
displayed'
be
sequence
ttte
Át
with
In
current
test
with
be
Present
exPansÍon
If
'
check
wirl
except
through
enables
'E'
RS232
down
the
synopsis
pass/fail
the
Press
be
can
conpletion
options
the
cases
some
conpletes
of
meg
4
if
The
RAM'
these
in
test
these
for
for
RAM'
the
'B'
Port'
arrovr¡
the
of
the
halted
of
of
there
and
)
Mega
Service
Manual
3.5
Testing

RAM TEST
Sumnary of
Tests
RAM is tested
64t¡, a¡rd
fron
0s, a counting
counting
counÈing
buffer
RAM
pattern (data=conplenent
pattern
into
the current
new
to a
until the top of
boundaries
of
each
is
64t Utoct.
in
to top.
64t
pattern
is copied
area,
RAM
checked
three stages:
verifies
by writÍng
If an error occurs,
the address, data
In
E.g.:
units
"
having nore than one ba¡rk
well as the bit
agree.
address as
correct chip.
the addresses and banks
O-7ffff
Soooo-rrrrr
written,
R2 45603E W:603E
The following table
520
bank 0
100000'lfffff
200000-3fffff
(A
bit
x 16
is
bank
chips--256k
=
a
16 Mbit
16 bit wide
x 16
=
2 Mbytes.)
or
The test
(data=low
word of
fron the top
J2
Kbytes
the
of
pattern,
is reached.
unique
the error
read, and the bits which did
data
R:613c bad bits:
position
gives
for
various
1040
bank
bank
group
UUit or
4
Vlega
0
bank
1
barrk 0
bank
of RAMs.
JL2k
2 kbytes,
low
patterns
used
the address)
of address
botton of a
and
video
RAM, then shifts video
and
niddle
are: all ls, all
low
repeats
(up
reverse
'
word).
Kbyte
J2
the test,
Finally, addressing at 64t
pattern
is displayed, followed by
code
(i.e.,
nust be used to find the
a
models:
2
0
0
A bank
bytes--or
in last 216
bytes
1,8".
1040ST, MEGA4)
correspondence between
Mega
4
bank 0
0
bank
bank 0
bank 1
nay
consist
of 256k
lMbit chips--lMbit
to
The
not
the
RAM ERROR CODES
Except where
corresponding to the
R0--1ow nenory failed while setting
Rl--failed walking
R2--failed
RJ--failed
address
64t< boundary
noted,
indicated bit(s).
1s
or 0s.
(counting pattern)
Controller.
Mega
n4--failed
Service
while displaying area
Manual
repair by
up to
test.
Probable failure
tested
3.6
replacing the
run
test.
.
(video
RAM).
in
RAM
Memory
Testing
chip

ROM TEST
Ttris
systen to deternine
(PAL
or
and the checksuns are
against known
deternine
there
128K
checksun expected for
may
ROltls;
The
2, French).
error is
set,
replace
or replace
New
incorporated
receive T0S revisions
will
be
COLOR TEST
This
displayed:
Each
band consists of 8
are represented, each
screen
a straight
involved,
The
lines in
sca¡r
outputs on the Video Shifter for that color, and verify the values
of the resistors on the output. Too
the nonitor
levels, making it
The
green
sunmed together by a resistor network to
(G0,
intensity for
The
on.
put.
The
is
twice that of
sumned outputs. For exanple,
Rl and R2 on
anplifier,
this resistor
in
later versions of the video shifter
which has
to
signal
pin
1 connected to a
BLANK
will be connected
test reads
the configuration
the version, tanguage/country,
NTSC).
AII bytes from
calculated.
value
good
if
be only
sone have
or bad.
two
test fails if
Incorrect
with
Six checksuns
ROMs
in
1
two
neg ROM'S).
the
checksun calculated does
the configuration
checksums are
displayed, replace
low ROM if
the
high ROM if
the
revisions of
any of H0, H1,
T0S
witl cause this
into the current version
before
necessary
to
verify
the
test verifies the Video
red,
green,
leve1s
blue, cyan, nagenta,
palette
(strips
should
líne
keystroke
operator
the display.
will cause
Video Shifter
G1, G2)
each color,
values of the
value of the
=
7 /8.
fron there to the video
and
network is incorporated into the full custon chip
part
nunber C101608
not
be discernable, but each color
across
the
screen).
intemupts
should see
If lines
nonitor
the
appear there are only
has three
and blue
(80,
depending
resistors
resistor
R2. This
this
allows us to
R0
signal then
line BLANK. Shifter with
pull-down
to diodes D9, D10, D11.
bytes
operating
checksuns for
system
These
of the operating
and
ROMs
are then
values are conpared
this version
are displayed,
the machine
(sone
machines have six
not natch
found
byte
indicated
the correspondÍng
any of
L0, L1,
or
or
test to
(e.S.
nessage. If
by a
ROM. In
L2
showed an
H2
showed an error.
fail if
of the diagnostic. If
receiving
checksr¡¡ns
diagnostic revision,
the
yourself.
Shifter. Seven color ba¡rds are
yellow,
intensity. All
of
is
a vertical strip across the
Because
will
that
cause
there
the display
are
nissing,
are
low
a brightness setting on
16 color
of the tight tining
to
gaps
no
check the three
not to distinguish between fine
four levels
outputs
for red
81, B2l. Each
give
on which of the outputs are
give
different weight to each out-
R0
at
on
is twice that of R1, which
get
8 equal steps on the
R1
and R2 off
,
passes
through a transistor
nonitor
(C101608).
or CO7O7I3
part
has
nunber CO259I4 will
resistor R144,10K,
being output.
(R0,
these
of
eight levels of
L/8, R0
=
connector.
Video shifter
pin
1
connected
and signat
TV standard
read
although
the
Version
a two
ROM
error,
not
you
and white.
palettes
should
jitter.
missing
or
R1, R2),
triples
off,
NOTE :
have
line
to
an
it
be
is
to
Mega
Service
Manual
3.7
Testing

Symtons
and
fixes:
Missing
1.
anplifier.
staircase
is
there,
backward
found.
Prinary colors
2.
Replace the
Coarse
3.
tra¡rsition).
output
color.
Specks or
4.
if RAM
Shifter.
Wavering
5.
place
interrupts
interrupts,
registers
interrupt
every
(pin
inputs at
the
(to
tne
MFP.
prinary
pattern
trace
to the
color.
is
06
blue,
(eight
forward to the
Video Shifter,
present,
Video Shifter.
change
of one
in intensity
Replace
Video Shifter
of the three
lines on the screen.
has
display,
every
(if
it will
during a
request
mícroseconds
L26
tested
been
horizontal
tine.
processor
the
The
not
horizontal
(pin
(2
20). If additional
pins
22-29 should all
Ufp) source
for the
output
Check
Q7
levels
the
green,
is
video
intensity).
of
until
secondaries
(not
a snooth
or
color
a¡rd
processor
outputs
This
is
lines
can
good,
not
is required
have
tÍner
time).
scan
32).
interrupts
There should be an
display
lines)
occur, locate the
be
interrupts
of the transistor
is red. Look for a
Q8
If the
connector,
faulty conponent
the
if
níssing or
dark to
for
look
for
be
a short
the appropriate
caused
by bad
replace the Video
occurring
nay be
in
getting
to handle additional
to change aII
Exanine
fron Display
high. If
is found,
no
replace the
signal
not,
trace
incorrect.
light
on the
RAM;
sane
the
extra
L6
color
MFP
the
interrupt
Enable
source:
external
is
KEYBOARD
first, and
keyboard.
is run.
comesponding
color).
screen.
the
arrow
indicates
keyboard
microcomputer,
Mega
Service
NOTE: if the
will be
TEST
Two types
keyboard
low, causing
of test are
if this
If multiple tests
The operator
character
The key
The
screen.
will
will also
mouse
Connect
flicker.
a short.
The self-test
nicrocomputer,
and scans
Mar¡ual
not
is
continual
run.
passes,
buttons a¡rd
the
checks comnunication
a screen
have been selected,
presses
the
on
be displayed
mouse
Any key clicks while the
and
the keyboard
connected,
intemupts.
The keyboard self-test
is displayed
keys and observes
screen
changes
four directions are also
nove
and
checks
RAM and ROM
for stuck
3.8
input to the 6850
the
representing
only the self-test
(reverses
in the
in
between
lower half of the
any direction
¡nouse
the
in the
keys.
is
that
background
shown
a¡rd the
is noving
CPU and
keyboard
Testing
done
t'he
the
on
the

KEYBOARD ERROR
CODES
KO--stuck
test was
K1--Keyboard
processor
keyboard
the
6850 is not functional.
K2--Keyboard
keyboard,
status. Replace
MIDI
through
is
correct. This
MFP
the
sent
MIDI
MO--Data
6850, through
input
key. A key
executing.
not responding.
and no
needs
to
status
on conpletion
the
TESTS
This
test
the cable)
chip. The LED
(not
all cables have
ERROR
CODES
not received.
the drivers,
of the 6850. Replace
closure
status
be
was returned
replaced
error. The
of
keyboard.
sends data
a¡rd reads
also
tests
in
the loopback
the LED).
Trace
was detected whire
A
connand
nas
within the
or the connunicatÍon
setf test
the
test,
out
the MIDI
fron
the input
the interrupt
the signal from
loopback
the defective
coûDand was
keyboard
the
port, (data
cable will
cable,
component.
the keyboard
sent to
the keyboard
allowed
channel
sent
sent
and verifies
fron
the
68J0
brink
the
output
receivers
and
tine. Ttre
through
to the
an
error
loops
back
the data
through
as
data is
of
to the
self
the
M1--ldrite/Read
data nisnatch.
the data read. Replace
M2--Input
noisy
MJ--Input
noisy
M4--Input
previous
the MFP
frane
error.
signal
parity
error.
signal.
data
byte
overrun. The
was
not responding
read.
Ttre
data b'ritten
6850.
ga¿
6850 or bad driver
ga¿
6850 or bad driver
6850 received
Probable
to the
bad
interrupt
6850,
request.
was not
or receiver
or receiver
the
causing
causing
a byte before
can
also
be caused by
same as
the
Mega
Service Manua1
3.9
Testing

RS232
TESTS
t'irst the
together
tested.
nethod
tra¡rsnission
receiver
and
lines
this
port,
& there
connector.
likely that
R5232
Data transmission
S0--Data
via
Sl--Daca
by the
Data
first, then
Data
is transnitted
is
chips.
are output
test
as the
does
RS,232 device
are
If
the
ERRoR
CoDES
not received.
1488 to J6
nisnatch.
is checked transnissing?receiving
no
the
integrity of
S2--Input
Probable
frane
MFP failure.
RS232 control
loopback
using
connect,or),
interrupts.
at
perforned
by the
Interrupts
by the
not
PSG chip and
thoroughly
nay
load resisters
passes,
test
1488 or
f489
error:
Check signal
pin
3
to
Data read was
the signal.
error.
Incorrect
lines
MF?
are
600,
a
300,
test
requÍre
in the serial
but the
pin
are
9
cfrips
MFP
May be bad
tine between
are
then
tested
(which
the data
using a
LãOO...t92OO
1488
the
and
function of the
input on the
drive
the
voltage
unit
bad.
path:
via
MF?
1489.
not what
driver,
MFP.
capability
swings
fails
pin
was sent.
receiver,
start
loopback is
bps.
f489 driver
and
MFP. Control
Note that
of
port
diagnostic
in
use,
8 to J6
and stop
are tied
polling
Data
of the
12 volts
it is
pin
Check
MFP.
or
bits.
2
S3--Input
S4--Input
S5--No
S6--Tra¡rsmit
S7--Tra¡rsnit
S8--Receive
S9-'RI/DTR
SA--DCD/DTR
SB--RTS/CTS
Mega
Service
parity
Probable MFP
data overrun.
previous
the
emor.
faÍIure.
byte.
IRQ. CPU did
GIue failure.
error.
MFP
error
intentionally
to cause
error
intentionally to
respond.
connection.
connection.
connection.
Manual
Input data
A byte
MFP failure or,
not detect
transnitter
interrupt.
interrupt,
an
interrupt.
cause
Signal
an
sent at
Signal
Sig¡al
10
3.
incomect
had
received before
was
interrupt
an
failed.
An
error
An
error
interrupt,
DTR
at
sent
at
sent
parity.
less like1y,
by the,MFP.
condition
MFP didn't
and
condition
the
and
is not detected
is not detected
DTR
is not detected
RTS
CPU read
the
failure.
GIue
MFP
was ereated
respond.
h,as created
MFP did
RI.
at
DCD.
at
CTS'
at
Testing
or
not

AUDIO
TEST
Outputs
channels.
a low
One cycle
nissing, replace
output
the
the
test
TIMING TESTS
fron
HSYNC,
tested. Tt¡e
RAIII
patterns
tests
error
the test
occur
the
printed.
TIMING TEST ERROR
TO--MFP
of the
nonitor
PSG
(these
These
the
chip wÍth an oscilloscope,
output
Ís being
tests
tests
nenu.
a¡¡d the Menory Controller video
video display
verifies
a¡rd
nay flash
which
Dessage
check the bus timing
is
passes,
and the nessage will renain. If
RS232
not
port,
tiner
generate
error.
the
to high
of each cha¡rnel
PSG
the
connector.
selected
both select the PSG).
run
are
Ttre MFP
sweep on each of the three
chip.
at
If
If
no output from
running
by
power-up
timers, the
perforned.
is
no sound is heard,
and trace the
printer
the
as well as
GIue
tining for
the
being selectable
display
redirects
test
that
the correct
on screen as this test is run. Tt¡ere
addresses are
for
printed
the
to the screen,
nessage
1s
erased.
display nenory
1772
the
then the test is run. If
and
If
not, a Bus Error
a terninal is
nessage
CODES
One
interrupt
an
or
not
will
nore
on counting down
be erased,
of the
four
but
tiners in the MFP did
sound
If
a
channel
verify the
signal
PSG,
port
verify
RS232
or
VSYNC a¡rd
counters are
throughout
generated.
are
PSG
chips. An
connected to
'rPass"
will be
is
to
Odd
two
will
Tl--Vertical
required
T2--Horízontal
required
T3--Display
generating
not
t4--Video
Sync.
tine
Sync. Glue
time
Enable. Glue is not
Counter Error. The nenory
the correct addresses
broken-up dÍsplay in
T5--PSG
T6--L772 Bus Error. The LlJ2
Mega
Service Manual
Bus Error. Ttre PSG
GIue is not
period.
period.
interrupt.
an
sone or all display
generating
is not
generating
generating
controller is not
for
the display. This
is
chip
chíp
3.11
defective.
is
defective.
vertical-
horizontal
DE
output
will
nodes.
sync
or
in
s¡mc
the IIIFP
generating
result fn
.-
ruu
f
Testing
in
the
the
is
a
lt)

DMA TESTS
\/o'
(2048
the
Four
port
sectors
test fixture via high speed
verified. Tt¡is test Ís
throughout the
DMA TEST ERROR CODES
DO--DMA
tined out.
GIue, or
processed
íf
the
with
causes
D1--DMA
counter error.
rarìge
Memory
by the
DMA Controller responds to
ACK.
Verify the
INTR output fron the
an
bytes)
repeated nany
RAM.
of
No DMA
occurred due
Controller, or the
MF?.
The failure can be
MF? by seeing that the HDII{T input
the nunber
incorrect. The Menory Controller or
D2--Data nisnatch
not
the sa¡De as the data sent.
problen persists,
the
emor.
opens a¡rd shorts.
7lJ2 is
D3--DMA not responding. DMA
resquest fron
FLOPPY DISK
loading the bus.
the external controller.
TESTS
Ttre
check the
A
third
controller
of data
MFP.
received fron
data
Replace
possibility
are h¡ritten to the RAM
DMA,
tines
then
read
for RAIII
back a¡rd
addresses
to faulty DMA Controller,
HDII{Î interrupt was not
isolated
HDRQ fron
the test fixture
by seeing
of bytes transferred was
DMA
Controller is bad.
port
DMA
the
DMA
the
data lines
is
could not respond
Replace
Controller. If
to the
port
that a defective
to a data
DMA
the
chip.
on
was
for
The Floppy Main Menu
Floppy
(I{ARNING
1)
disk drive
Quick
--
Test
2) Read Alignnent Disk
Disk
3)
4
5)
6)
7)
In
1.
)
Interchange
oist<
E;<erciser
Check copy
Test
Speed
InstaII
single test
Quick
reads
a¡rd
test.
tracks
rvrites
overwritten.
drives are online and
assure that the drive are correctly tested, the
operator should
test. Once the
will
and
size).
Mega
Service
Manual
routine
all choices
Test
protect
disk dríves
noder
For
0,
track
If
displayed on the nenu screen
be
(80-82)
disk
79
if
they are
(nenu
run,
2,6,7
of side 0.
write to the disk)
installed, fornats,
If double
1
verifies
and
installed,
double or
that side 0 was
checks to see what
single
writes, and
sided,
option 6) before calting the
the drives become
sided.
installed,
except
tracks
r¡enu is displayed showing seven options:
a
each
L,
and
of side
79
no
disks are
install
test is
(below
3.72
fornats
the
Testing
not
To
RAM

2.
Read
track.
Continuously reads
with an analog alignnent
input
a nunber, the default
by the
operator.
diskette.
If
"Return"
is
track 40.
track,
a
for checking
The
track
pressed
is
alignment
be read
to
nay
without entering
be
Interchangeability test. Checks to see
3.
disk drives each can be
Disk exerciser.
4.
on the disk
Copy Protect Tracks. Tests tracks 80-82,
5.
softrùare conpanies for
some
are cause
drives will
Test speed.
6.
for
for replacenent because sone
not
A nore
a¡r
write to these tracks.
The rotational speed of the drive
displayed on the screen
acceptable
lowest
key is
InstaII
7.
If nore
floppy nenu will
range is
values
pressed.
disks.
than
not
measured are displayed.
Specify
one test
appear,
read
by the other
thorough disk test;
indefinite
period
protection).
copy
as the
196-204 nitliseconds. The híghest and
how nany and what type of disks to test.
is
selected
but the
Quick
autonatically.
FLOPPY TE.ST ERROR
No floppies connected--the
The
cable
pohrer,
or the
CODES
nay be
drive
controller
inproperly connected,
is faulty.
if diskettes
of tine.
period
The
from
the
Test
cannot
or the clrive
fron two
disk drive.
tests all
which are used
Not all
nanufacturers disk
sectors
failures
Ís tested and
rotation.
of
test stops
when any
nain nenu, the
will be selected
read
:Lndex
pulses.
has
by
The
no
F0--Drive
resLore
to drive. Verify
Listen for the sound
diskette should
1772')
of the
interrupt to the
asserting
light), check the
is
selected.
F1,F2,Fl errors of
nessage now says
and displays
errortt.
Mega
Service
not
selected.
(seek
track 0).
to
the
open).
go
should
Iow.
7772. If
INTR.
If the drive
PSG chip.
selected, and
not, replace the
If
previous
"Error
nore
a
Manual
Drive
light
of the
If
If
installed, but
was
Check cornection of cables,
front
the
on
head
seeking
this occurs,
all
so,
check
for
none, replace the
MFP,
verify
that
is not being selected
pin
19
versions
liriting"
specific
3.
Pin 20 should
should
PSG.
emor
13
go
have
(or
failed attenpting
of the
an
drive
(the
slide
(pin
TRO
interrupt on
1772. Else trace
MF? responds be
the
go
low when drive
low when drive
deleted.
been
reading or
nessage, €.8.,
formatting),
pourer
goes
on.
on the
23
The error
on
pin
B
CRC
"F9
Testing
the
28
the
(no
is
A

F4--Seek
t,l:e
but
error.
1772
Verify that the
are
sent to the drÍve. Probable failure
the drive is
also suspect.
STEP,
MO,
and
DIRC
outputs
in
the L772,
fron
Fl--lirite
If
during
not,
F6--Read
supposed
diskette,
F7--DMA
DMA. Replace
FDRQ
high
reset
not,
protected.
0K, verify
the test; if it is,
problem
the
compare
to be
disk drive, L772,
error.
whÍle running
with
each data byte
button
trace RESHI
still stuck, replace
F8--DI{A
F!--CRC
FA--Record
count
not fix
error. Replace
it, replace
error. The
Ehe 1772.
not found.
be
a bad diskette,
but not
not
drive
A).
Check the
that the ldP input
is
with the
error. Data read
written. Check in
DMA
Controller
DMA
the
could
Controller. If
the test. It
transfemed. If
a¡rd verify
to
diskette
The L772
B,
Ehe
its
E}r'e
DMA
the
or disk
drive
1772 is
that
source.
1772.
the Memory
could not read
or
write
and
protect
(L772 pin
the 1772 Is
then
drive.
disk
from
the
DMA Controller.
not respond
should nornally
(L772
MR
If MR
Controller,
Controller.
drive
L772. If
not
at
tab on the
2l) is
defective;
disk
was not
the following
to a
emor
pin
nay
the test. fails
fault
persists,
be low
stuck high,
goes
13)
is
0K, but FDRQ
be bad,
a
sector
(likewise
diskette.
going
low
what was
order:
request
check
and
push
low.
for
go
the
If
is
if
that does
else replace
header.
May
drive A
fails
if
B
Mega
FB--Lost
1772
passes,
also be
FC--Side
select
both
sides of the
to
be overwritten.
FD--Drive
Probably
Could
Soft Error
Hard Error
Service
Manual
data. Data
could tra¡rsfer
the tJl2 is
fault.
at
was transferred
to the
probably
emor--single sided
diskette, but writing
not ready.
a
bad disk drive. Verify
also be a faulty L772.
does not
=
fail
failed
=
of the
fornat
!
The fornat/write/read
cause a failure
a second time.
second
retry.
following:
errors.
14
3.
to t}:e L772 faster
DMA
Controller. If DMA
bad.
The DII{A
drive. The test tried
side
operation
by checking
after 1 retry.
)
Unit
20 read
halt if
will
errors, 20
than the
Port
Controller
to
1
caused side
timed-out.
another drive.
(If
doesn't
you
reach any
write errors or
Testing
test
could
write
0

PRII.ITER AND
JOYSTICK
PORT TF"STS
port
The
port
on
outputs data on the
joystick
and
the test
fixture and reads
test fixture
joystick
connecting the
reversed,
Po--Printer
what was written. Verify that
(pins
the RS232 test.
chip
-
selects are being activated
the
If
J1l
is
PSG.
P1--Busy input
data
or the
port
6-13) are toggling
is
PSG is
the data
(Joystick
good
by testing
the STROBE output
Joystick 0
occurs, see
amiving at
the test
fixture
test
ports.
parallel port,
to the
Joystick
in response
joystick
printer
PRTNTER/JoYSTTCK ERRoR CoDES
and
error.
If
probably
selected and
the
not being
lines toggle, verify
pin
0)
error.
3
another conputer.
The
fron
pin
handling
MFP
is not connected.
I
pín
22 fron
fixture may be bad. Verify
is
used to test
parallel port
The
back data.
which
ports.
to connands
ports
to the test
joystick
Data read fron the
the
when
the test
RI-DTR
and
The
is
The keyboard
from
tests will
data
DCD-DTR
selected.
and
not
outputting signals,
the
2ütlz
continuity.
pulled
is
up. Verify the test
If it is
input
the
to the
PSG
MFP is
is not
If
for
that. Othervise,
J5
pin
11. If no signal at J5,
with
paralle1 printer
the
writes
test
joystick
directed through
CPU. The
the
a latch
to
port
reads
cables
test
the
the
fixture nust not be
fail.
printer
lines
port
on the
was
PSG
not
chip
is run. If not, run
errors occur, the
Check if
cLock
is
the chip
present.
If
replace it.
AIso verify
that
fixture
replace
0K,
not being
read,
the
or
functioning, or
P0
the
look
error also
for
a signal
another conputer.
JO--Joystick
Busy input
the
pins
Jl--Joystick
Busy
the
pins
Port
keyboard. If error
1,2,3,4
Port 1. The
input error occurs,
keyboard. If
1
,2,3,4
J2--Joystick time-out.
outputting data on the
test fixture to the
detected
This
keyboard faílure,
faulty
by
error ca¡¡ be
test
this elininates
Mega
Service
Manual
keyboard input is not functioning. If
Ttre
0.
error occurs,
to ltZ
pins
keyboard input is not functioning. If
error
to ttZ
pins
Joystick
joystick
keyboard and sent to the CPU via the 68¡0.
the
caused by
keyboard-CPU connunication line, or a
fixture.
any
If
problen
3.r5
fix
persists,
12,10,9,8 respectively.
fix
persists,
J,5,4,1
printer port
printer port
the
with
first.
that
check continuity
first.
that
check continuity
respectívely.
inputs
and routing Ít via the
ports.
porter-up
keyboard-CPU
othervise,
otherwise,
rdere si¡rulated
Joystick
failure
keyboard
replace
fron J11
replace
fron J11
inputs
(code
test
communication.
passes,
Testing
the
the
by
are
P0),

J3--Left
0therwise
continuity
button
replace
from J10
input.
If Pl emor
keyboard.
the
pin
6 to ltZ
occurs,
0n the
pin
11.
fix
520ST,
that
first.
also check
J4--Right
button
Otherwise
continuity
HIGH RESOLUTION
If this test
message
a
waits
received
the
is
displayed
for an
interrupt
(the
dÍsplay to
horizontal and
reverse every
will
is
correct,
nonitor
RGB
GRAPHICS
he
a¡rd
CHIP
This tests the
around and
appear
(G0-G13)
chip.
REAL-TIIúE CLOCK
A faulty
perform
on the screen.
but the
,
input.
replace
fron J10
MONITOR
is selected
operator
high
vertical
two seconds.
unplugs
the display
(BLiTTER)
abÍIity
logical operations
action
BLiTTER
Pl
If
the
pin
emor
keyboard.
6 to JtZ
while a color
connect the
to
from the
connects the
MONOMON
nonochrone
resolution.
lines, each
ltlhen the
nonochrone
the
should
of the
Ma¡ry different
for
may
cause
return
BITBLiT to
any emor
BUS
a
fix
occurs
0n the
pin
nonochrone nonitor. The
input
,
520ST,
6.
monitor
to the
that
is
MFP, and when
nonitor),
first.
also check
connected,
changes
Ttre display screen shows
pixels
2
nonitor and
on the
error
is the sa¡ne:
ERROR.
in
width.
operator sees the display
nornal.
to
Eove blocks
data.
messages are
Ttre
screen
re-connects
of nenory
patterns
No
possible
replace the
CPU
the
The test saves
time, waits
etc.
have all
verify all
EXPANSION
This
fixture
test
software,
interrupt
and
the CPU are
after
Three LEDs will
BGACK
expansion
floppy test are
toggling.
Mega
Service
one second,
registers.
CONNECTOR
test,
(the
top cover
fixture).
the
and
lines are tested
tested
the systen
(bus
grant
connector
A lit LED
Manual
current
the
and
rolled over.
modeJ.s,
Mega
for
and shield
It tests the
renainder
with the
is
turned
remain
acknowledge).
run.
neans the
on and
lit:
is run
test
The LEDs sinply
time and
verifies
is repeated
The
requires the expansion
must be
expansion
by LEDs.
in
software.
LEDs.
BR
line
3.t6
Most of the
the
(bus
These should
and
is not changing.
and writes a
minutes, seconds,
that
date,
hours,
for a¡rother
renoved to
interface,
The data and
The
control
LEDs will
Inenu appears on the
request),
(2)
either
BG
go
off after
indicate that
install Èhe
in
address busses
(bus grant)
DltIA test or
the
the
new
date to
test
part
by
lines fron
go
off
screen.
and
(1)
the
line is
Testing

The software
bus,
and
tests
interrupts.
three
groups
signals:
of
bus, address
data
The first
setting
one bit
lines. If an
displayed.
The second
across address
RAM
If an error
byte" or
on
create
and
the test
on
I'EX2
whether
The third test
interrupt
INT7.
expected,
errort',
ERROR
or
CODES
Ttris
occur
INITIALIZATION
11 RAM
when
data
test
high
error
test
bits
fixture to check
is found, the
external
the error
uses
requests.
If the
then a
ttEXl
QUICK
is a
running the
nessage Ís displayed:
INTJ errortt.
REFERENCE
brief
(Errors
is stuck.
line
L2 RAM disturbance.
location.
RAM
13
14- MMU error.
I5
.
RAM
addressing.
sizing
DTACK after
No
error.
T6-
writes
at a
and
tine, to
is found, the
writes an
O-1!, then
message
RAM emor,
occurred
in
circuitry
There
appropriate
sunmary
diagnostic.
occurring
Location
Wrong
Uppernost
is
location
RAM access.
check
RAM on the
for open
reads the
nessage
increnenting
across
address
for open or
external
"EX1
high byte"
low or
the
on the
are
external
three
interrupt
"EX3
all error
of
before
altered
the
by write
is being
address
faiLs.
test
or shorted
bad
"EXO
pattern
16-23 to
bits
shorted
is
address
RAM error'
printed,
high address.
test
interrupts:
does
not
INT3 error,
code
title and
to another
addressed.
fixture,
data
bit"
is
(0,1,2,...1
the
bits.
low
depending
fixture
Il.¡T3,
occur
menu appear)
IlfT5,
"EX4
which
5
when
INT5
nay
V*,
to
tr
rrirl-
6
LU
!
¡'')
u¡ò1
tJ
"¡4
i4
Mega Service
EXCEPTIONS
El--E5
not used
E6 Autovector
E7 Spurious
Device
EB Internal
E9 Bad
Instruction
EA Address
address
address.
or bad
.--EB
Bus error.
externally
Displays
Manual
(may
occur
error.
at any
IPLO
interrupt.
interrupted,
Exception
Fetch.
error.
or
Tried
read or write
Usually
instruction
Generated
GJ-ue. Usually
by
address of
the
tine)
grounded
is
Bus
error
to
not
read
word
but did
(generated
this error
fetch.
internally
caused
the device
3.17
or 68000
during
by 68000).
exception
provide
instruction
an
or
preceded
is
by
being accessed.
is bad.
processing.
interrupt
vector.
from an odd
long word at
by a
by
device
the 68OOO
bus emor
not responding.
an odd
or
Testing

RAM
R0 Emor
execution.
Rl Error
R2 Address
line
R3 Address
R4 Error
KEYBOARD
K0
Stuck
K1 Keyboard
KZ
Keyboard
MIDI
in
in RAM
low
chip.
nenory
error.
not
working.
error at 64k boundary.
during
key
video
controller is not responding.
controller
M0 Data not received.
Ml Data received
M2 Data
M3
M4 Data
RS232
input franing
Parity
error.
overrun. Byte was not read fron
byte
arrÍved.
is not
(first
Bad RAItl
RAM test. Bad
error.
chip
reports
what was sent.
2K),
or
error.
possibly
memory
RAM
chip.
the 68!0
affecting
controller.
before
program
Address
next
5r''
il
>
Data not received.
S0
51 Data received is not
52 Data input franing
Parity
53
54 Data
error.
overrun.
Byte
what was sent.
emor.
not read fron
was
byte arrived.
55 IRQ. Ttre MFP is not
receÍve.
Tra¡rsnitter
56
No interrupt
57
No
58
interrupt from receive
59 DTR--RI.
connector.
SA DTR--DCD.
SB RTS--CTS.
DMA
D0 Time-out.
Dl DMA
count eror.
Controller
error--MFP.
fron
These signals are connected
Changing
Same as 59
Sa.ne as 59
DMA did not take
error.
generating
transnit error
error
DTB
does
for
these signals.
for
these signals.
place,
Not
aII bytes arrived. Possible
D3 DMA Controller not responding.
MF?
the
interrupts for
(MFP).
(MFP).
not
cause change in RI.
interrupt
or
before
the
next
tra¡rsmit or
by the loopback
not
detected.
Menory
Mega
Service
Manual
3.18
Testing

TIMING
MFP
T0
timers
T1 Vertical sync
Horizontal sync
T2
T3 Display Enable
failed.
timing
tining
Interrupt
T4 Menory Controller
T5 PSG
Bus
the data
T6 1J72 Bus
data bus
the
PRINTER
AND JOYSTICK
P0 Printer
Pl Busy
(printer port
J0 JoysÈick
J1 Joystick
Joystick
J2
Left button
J3
Right button
J4
FLOPPY
FO
DISK DRIVE
Drive offline.
test.
bus too
test.
port
port
port
(keyboard
PSG
L772
too
error.
0 failed.
failed.
1
line failed.
line faired.
Not responding to
F1 Format error.
(Note:
now
specific
former
will
F2,F3 write and
say
"error
error
found.
failed.
failed.
failed.
video address
is
chip
long.
chíp
long.
PORTS
causing
is causing
input) failed.
controller)
read emors
writing"
)
counter
a bus error
a bus error
timed-out.
restore
are deleted.
reading]
[or
failed .
(seek
and
ltt - ¡r--^\
4'^
a
i'
b
ö
by staying on
by staying on
track 0).
The nessage
display the
wJ
'
F4 Seek emor.
F5 ['irite
Data conpare.
,F6
DMA error.
n
FB DMA count
F9 CRC error.
FA Record
Lost data.
FB
FC Side select
FD Drive
Mega
Service
protected.
error
not
ready.
not
Manual
(Data
found.
error.
read
(Menory
Tined-out
not equal
Controller
perforning
3.r9
to data
counLer.
the command.
written.
)
)
Testing


Top Cover Removal:
SECTION FOUR
DISASSEMBLY/ASSEMBLY
MEGA/ST DISASSEII{BLY
1) Renove keyboard
2) Turn unit
Renove
l)
the top case
is
to be exposed,
renove
the disk
Turn
4)
stightly fron
underneat its
renoved
Upper
Shie1d
1)
Straighten
located
2) Lift
be free from
Push
3)
shield out of the botton cover and
Disk Drive
Removal:
connector fron the
upside down.
the
screws fron
9
to the bottom. If
the square holes. These fasten
side of the
the
or the disk drive is
the three screws fron
drive Ín
place.
the unit upright.
the back,
left rear
easily.
Renoval:
the six twist tabs.
under the disk drive.
the shield up fron
anythings
in
l{hile
unplug the battery
corner.
the
the
the
lifting
back
rear.
round
Note
gentlely
the disk drive up while lifting
pull
top cover.
printed
cÍrcuit board
to be renoved,
ho1es. Ttrese hold
the
top cover up
connector fron
Now
the cover
can
that there ís
so
up the front of top
forward.
that
it will
also
be
one
Mega
1) Lift
Power
Supply Removal:
1)
2)
3)
Service
the disk drive
connector
Remove
Unplug
corner of the
Lift
ManuaÌ
and the
the
the wire
poh,er
the
2
slightly and unplug
ribbon
screws at
harness
poh,er
supply up out of the
cab]e.
front
supply.
corners
connector in
4.r Disassenbly/Assembly
of
main
power
the
power
the
assenbly.
harness
supply.
right front

Renoval of
If
1)
the
2) Renove the
botton
Lift
3)
main assenbly
power
power
supply
supply
six
case.
the assembly
fron botto¡n
has not
renoval
studs
already
whÍch
from the
up
section
case:
been
to
secure
front and
renoved,
renove
the
it.
I/0 shield
then
pull
follow
the
to
fon¿ard.
Renoval
1) Straighten
2)
3)
of Shield
twist
Renove the
Note:
convenient
a¡rd
side
tabs away
Now
disk drive
if those
the
Lift
Printed
Fron
six
twist
tabs.
fron the
I/0 shield
najor conponents
the
that
configuration
may be
components
printed
circuit
It
back.
Board:
nay be
slightly.
necessary
are exposed,
Circuít
board
in the
for troubleshooting.
re-connected
needed.
are
assenbty
and
away
pull
to
this
keyboard
The
placed
off
fron botton
the
is a
to the
shield.
I'tega Service
Manual
4.2
Disassenbly/Assenbly

Mesa/ST
RE-ASSEMBLY
1) Place
2) Attach the
on
Place the assenbly
3)
4) Secure
PIuS
5)
with tabs
etace
6)
Fasten the
7)
corners
supply shield
insulation
top of
the
power
in
assenbly
with tno
I/0
Botton
I/0
in slots.
power
hold the scree,,
Plus disk drive
8)
go
under
Push
t)
the
10) A1ign tabs on
fit
place.
in
shield),
the battery
rear
left
shield over
top
panel
shield
Shield
on botton
to the
over
Ín lower
shield
supply
in lower
in
or by
power
corner
bottom shield
to the
connector
plastic
supply to the botton case at
screws.
place,
and
corìnector
Tttis
using a
renoving the shield.
ribbon cables
and
position
up
of the
nain
assenbly.
shield.
ports.
I/0
insulator
plastic
botton case with the 6 studs.
case.
position porr¡er
and
case.
be done with the
car¡
magnestized
drive over standoffs.
fron the
top shield.
with slots on top
Twist
Place
panel.
screwdriver
into
drive
opening
the tabs
Main Board
supply
front
both
power
(cables
located
shield
lock
to
to
in
and
Mega
11) Place the top cover
12) Turn over the assenbly
longer screhrs
drive.
It is strongly
plastic
in
there are
and
Service
Manuaf
to
no shorts to
reconnended
nalce
sure
over the
go
into
A h¡ORD OF
that
Shield.
assenbly.
replace
and
round holes
the
CATITION
the
screws.
9
to secure
that the conputer be
re-assenbly
the
4.3
was done correctly
The three
the disk
retested once
Disassembly/Assembly


SECTION
SYMPTOM
FIVE
CHECKLIST
This
their
troubleshooting
on
Troubleshooting
Sympton
DISPLAY
Black
White
Dots/bars
screen
on
color
One
Scra.nbled
T.V.
section
probable óauses.
nost
PROBLEMS
screen
screen
nissing
screen
output
bad
gives
in this
Guide.
Probable
No
Shifter.
a
Video
Controller,
with
RAM,
diagnostic
video
signals
Glue,
cartridge.
Ir{odulator,
with
a
power
Dead
Shifter,
Menory
your
For
summary
nore
brief
docunent,
Cause
(check
See
LED),
TESTING
Unit".
Glue,
68000.
terninal
Controller,
cartridge.
sunner,
oscilloscope.
$rith
Menory
Contro1ler.
phase
oscilloscoPe.
of
detail,
of the
bad
section,
Menory
Use
connected
buffer,
locked
loop.
comnon
refer
problens and
the
to
Diagnostic
GIue chip,
"Troubleshooting
Controller,
diagnostic
RS2l2
via
Video Shifter.
Use
Trace
Shifter.
the
Video
section
Cartridge
Video
bad
DMA
cartridge
port.
Use
Check
diagnostic
signal
the
DISK
Disk won't
won't
Disk
Systen
Ioading
Mega Service
boot
PROBLEMS
Power
chip,
supply,
disk
DRIVE
if not,
spinning.
drive
disk
working,
diagnostic
the
fornat
crash
files
after
FDC(1772),
Diskette,
Menory
the
Controller.
âiagnostics
Controllèr,
drive.
Manua1 5.7
drive.
check
not,
If
or
check
DMA
disk
Menory
(1772),
FDC
if select
See
outputs.
PSG
check
external
an
try
Controller
DMA
cart.
Controller,
dríve,
Swap
check
to
Controlleri
Controller,
DMA
Listen
power
the
drive.
and
disk
FDC
ß772),
diskette,
FDC
or
Synptom
light
goes
for
supply.
L772
drive.
DMA,
retry.
(L7721,
replace
Checklist
If
PSG
on'
Eotor
Swap
not
with
ot
Use
DMA
disk

Systons
Probable
Cause
KEYBOARD
Keys
won't
Keys won't
nouse
but
UIDI PROBLEIUS
No
data Bad
RS232
No
data Bad
PRII.ITER
No
output
Does
not
to
a specific
PROBLEMS
work Bad keyboard
work Keyboard
does
PROBLEMS
PORT
output Input inpedance
printer
powered,
, 74LS05).
+/-
lsolate
PROBLE}IS
PSG,
Bad
,nodify
controller, 6850,
cable was
recycle
opto-isolator
68901 MFP,
12v
supply
bad line(s).
MFP
receiver,
is
chips.
of
pullup
resistors
MFP.
inserted
power.
white unÍt
chip, 6850, inverter
driver,
blown.
printer
on
is less
or
Use diagnostics
than
printer.
PSG
was
(74LS04
chips,
to
ohn
lK
Does
Does
Does not
after cold
No
is inserted
Does
Mega
Service Manual
DMA PORT
not
function
REAL
TIME
not
function Bad
save tine Bad batteries,
boot
BLiTTER
vídeo
PROBLEMS
when Blit
not functÍon
PROBLEMS
Bad DMA Controller,
(loading
CLOCK PROBLEMS
RTC PAL
Junpers
nust
be cut before
Replace
problen.
the bus).
chip,
below
blitter
5.2
clock
power
a¡rd
blitter
chip
Menory
Controller,
chip, crystal.
off
sense circuit.
right
to
will work.
if
above step
Synptom Checklist
of blitter
doesn't fix
L772
chip

This
in
taken
The
context
problems
ôartridge
user
troubleshooting
necessary
flowchari,
where
result
troubleshooting
details
of
in which
for which
is covered
would
Atthough
in solving
reading
necessary,
in repair
DIAGNOSTIC
sectÍon
using
the
the
the
in the
all
run
guide,
thorough
a
sone
the
and swapping
the
of
SECTION
sumnarizes
the
SIX
FLOII¡CHARTS
using
Mega
cartridge
cartridge
cartridge
would
would
troubleshooting
the tests,
the
take
and
understanding
problens, in
docunentatíon
out
Problem.
diagra.natic
in
the
not sho$m;
are
be
not be
look up
action
of
most cases
the
on
indicated
the
forn
diagnostic
this
used,
including
useful.
guÍde.
In
errors
reconnended.
syste¡n
the
following
diagnostic
conponents
steps
the
cartridge'
of
the
sone
the
shows
Usage
general, the
the
in
be
may
the
cartridge
will
(if
more than
kno*n
whether
system
good
Extreme
circuit
easily
can
plastic
where
part.
first
the
has been
Handting
care
chips.
be
carriers
Replacement
replacenent
indicated,
is
one
other
If
part
is
rePaired.
of
should
They are
damaged
or
by
conductive
on
Procedures
indicated,
is
components
good
by
Integrated
taken
be
sensitive
very
careless
replace
later
are
replacing
Circuits
handling
when
to static
har¡dling.
when
foan
replace
at a
one
replaced,
in
the
Keep chips
in use.
not
conponent
the
time)
systen
the
with
once
integrated
electricity
in their
a
verify
the
and
Mega
Service
Manual
6.t
Diagnostic
Flowcharts

START
CONT\ECT
TERM¡NAL
TO RSæ2
CYCN-E POWER
DISPLAY
TEFINô.¡AL
DAGNOSTIC
FEPLACE
PER
DIAGNOSTIC
GUIDE
PORT
ON
?
PARTS
IS DISPI.AY
RE.ADABLE
REPLACE
PARTS
PER
DIAGNOSTIC
GI,JDE
CYCLE POWER
?
TESTS
ALL
RI.}.¡
ERROR?
Mega
Service Manual
MEGA/ST DIAGNOSTIIC
6.2
FLOtll
CHART
Diagnostic
OTHER?
Flowcharts

NO ERROR ON
DAGNOSTIC
RUN DISK
DAGNOSTIC
OR
REPLACE
DRIVE
PROBLEM
FOLAD
CON¡TACT
TECHNICAL
SUPPORT
?
ATARI
TRACE
FROÌ\, VDEO
APPROPRIATE
CONTINUOUSLY
SIGNAL
SHFTER
OTJÏPUT
RUN
TEST
TO
Mega
Service
MEGA/ST
DTAGNoSTTTC
6.3
FLoW CHART
Diagnostic
Flowcharts

NIO
ON
OR
DISPLAY
ìvlOÀtTOR
TEruINAL
t€
FEPLACE
GLUE
Fts232
DISPLAY
\
t/t/
t€
TN
\'
1. CI€q<
2. REPLACE
OSCILLATOR
1. GLUE
2. ltlBMORY
SHIFTER
FIEPLACE:
CONTROL
3.
CPU
FEIVIOVE
NSPECT
TEST FOR
SI-{OFITED
SHIELD
PCB
+
5
V
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2 REPLACE
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SUPPORT
Mega
Service
PCB
ATARI
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REPLACE
PER
DIAGNOSTIC
GUIDE
PARTS
6.4
Diagnostic
Flowcharts

NO
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RESTART
REPLACE
SHFTER
RESTART
Mega Service
Manual
MEGA/ST
REPLACE
tì/EMORY
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DrAGNoSTrrc
6.5
FLow
CHART
Diagnostic
RESTART
Flowcharts

PARTS
SECTION
LISTS
AND
SEVEN
ASSEMBLY
DRAWINGS
Mega service
Manual
7.I
Parts
List
Drawings
&

MEGA PARTS
LIST
PART
NUMBER
cA200055-00
cA200093-001
cA200008-001
cA200018-001
cA200022-001
cA200025-00L
cA200039-001
cAz00040-001
cA200041-00L
cA200042-001
cA200043-001
cA200054-00L
c070350-003
c070352-003
clû3047-001
cAo70025
DESCRIPTION
1
PCBA
PcBA
MEGA
MEGA 2/
MEGA
MEGA
MEGA KEYBOARD
MEGA
MEGA KEYBOARD
MEGA KEYBOARD
MEGA
MEGA
FDD
FDD uNrr
FDD uNrr
STM1
cAP
CAP 39pF
cAP
CAP 150pF
cAP
cAP
(l¡le
(1Me
POWER SUPPLY
2 CASE
4 CASE
KEYBOARD CASE
KEYBoARD
KEYBOARD CABLE
uNrr
MOUSE
30pF 50v
100pF 50V
330pF 50v
1000pF
cAP 0.1pF
cAP
O.221tE
CAP 0.47¡:F
cAP
4.7pF 25V ELEC
cAP
10pF
cAP 47ytF
cAP
100pF 16V
cAP
1000pF
cAP
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cAP
L00L¡rF
cAP
5-30pF TRIMMER
RES O OHM
RES
5.1
RES
27 OHM
33
RES
RES
47 OHM
RES
75 OHM L/AW
RES
1OO OHM L/4W
RES
].50 OHM
RES 220
RES
470 OHM
RES
].K OHM T/AW
RES 1.2K
no¡¿)
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4
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5% CARBON
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AXIAL
AXIAL
AXIAL
RADIAL
AXIAL
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RADIAL
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CARBON
CARBON
59" CARBON
AXIAL
AXIAL
AxrAL
AXIAL
AXIAL
LOCATTON
SUBASSEMBLY
SUBASSEMBLY
SUBASSEMBLY
SUBASSEMBLY
SUBASSEMBLY
SUBASSEMBLY
SUBASSEMBLY
SUBASSEMBLY
SUBASSEMBLY
SUBASSEMBLY
SUBASSEMBLY
SUBASSEMBLY
SUBASSEMBLY
SUB
FOR
ABOVE
SUB
FOR
ABOVE
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c39,40
c54
c43-46
c28
c29
c68,69
cL,2,5-7
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42
,47,49,50
56,57, s9,60
70
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24
,
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37
,
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,

PART NUMBER
DESCRIPTION
LOCATION
c070567-004
c070 1 59
c070
448
c014384
c070205
c070471
-00
-001
6
c07047L-002
c0?0790
c07024L-002
cl01805
c025993
cll0232
c1 00281
c010L29
c070130
c070131
c070134
c070033
c070445
3
-00
1
1
c070644-0 L
c10028
c070120
c070119
cAO70024
cAo70023-003
cA200053 -002
c]_01_643
c025982
c025913
c025915
c0259L4
cl0 160 I
c0259L2
c025986
c025981
c025983
c025984
c025985
cr0L7t2
c025988
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3.3K
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4.'7K
RES
5.1K
RES
lOK
RES
12K
RES
51.K
RES
NET!{ORK
RES
RES NETWORK
NETWORK
RES
INDUCTOR
INDUCTOR
INDUCTOR
INDUCTOR
OHM
OHM
OHM
OHM 1/4W
OHM L/AW
OHM L/4W
OHM
FERITE
O.27UA
L0pH
220¡tH
LINE FILTER
NOISE
TRANSISTOR
TRANSISTOR
DIODE
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CRYSTAL
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CONN
CONN
CONN DB-25S
CONN 13
CONN
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SOCKET
PUSH
FLAT
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rc
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NUMBER
DESCRIPTION
LOCATTON
cL0L62t
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c101.625
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630
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Mega
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GLOSSARY
SECTION NINE
OF PART
NAMES
AND TERMS
the
source
graphic
patterns
and destination
chip which is
block
and
BITBLiT--Atari
used to tra¡rsfer
with
between
transfer.
BUS
ERROR--GIue
there
to
memory
an illegal
causes
CPU--the
is
a device not responding
68000 microprocessor.
DMA--direct
from
external
but the Menory
exception
has
problem
a
access
¡nenory
asserted BERR
with
(attenpting
processing.
access. Process in
storage device to RAM,
storage. Transfer is
the CPU,
place.
DMA
CONTROLLER--Atari
process.
EXCEFIION--a
so the CPU
Glue
arbitrates the
All
disk I/0
state
proprietary
in
activity, saves what it will
later in RAM, fetches
executing at the address
processing
doing
by intemupts, instructions,
Section Two,
is
done, the
before the exception
Systen
detail.
actually
memory
of
a combination
which
to
the
current cycle. This
(for
Controller fails
to write
very fast,
can be
processing
bus between the
chip which
goes
through
which the
a vector
processor
need
(address)
vector. When
processor
occurred.
or
Errors,
or a 68000 reference for nore
DMA
a
from
a source to destination
of any
was set up
inforn
exa.nple, CPU
the
device.
logical
prior
processor
could be due
tries
to assert DTACK),
ROM).
which
or
takes
to
data
from RAM
place
A bus
is
independent
while DMA
CPU ar¡d DMA.
controls
this device.
stops the
resune
to
from RAIft,
the
the exception
will
continue what
Exceptíons
emor conditions.
can be caused
It is
operations
to the
that
read
to
op
error
tra¡rsferred
to external
of
is
taking
DMA
the
curent
acbivity
and starts
it was
See also
GLUE--Atari
HALT--state
Mega
Service Manual
proprietary
chip which
timing and control signals.
j-n
which the CPU is idle,
high-inpedence state,
input.
externally
closure, and
This
by
is
a bi-directional
RESEtr
the
internally
double bus fault is
to
handle
prevíous
a
and can only
circuit
an error during
error. For
occurs, and during the
error, another
HALT.
bus
error
9,1
ties together
pin
on
when
a double
exception
occurs,
all bus
on
power-up
a sequence
sxamplê, if
processing
then the CPU will
lines
be ended with
the CPU.
bus
are in the
It
reset
or a
fault
which
a bus emor
for
aII system
RESET
a
is
driven
button
occurs. A
is run
the bus
assert
Glossary

HSYNC--timing
horizontal
iretraci.ns).
microseconds)
CPU.
the
signal
ðcan
also
for the
is on
The
is
video
the
display.
screen,
and
synchronization
IPL1,2
encoded
onto
Deternines
when
it
(approx'
as an
interrupt
when
is blank
every
the
63
to
II,ITERRUPT--a
is doing
of
they
tevèl of
MFP
interrupts.
Interrupt
Operation,
MEMORY
accesses.
Subsysten
MIDI--Musical
by
lógical
consists
chips
interrupt
request
perforn
a¡rd
exception.
ignored
be
will
CPU.
the
interrupts,
Interrupts
Priority
Main System,
CONTROLLER--Atari
see
for
Instrunent
which
electronic
sysgen
of a
(74LS04,
channel.
MFP--MuIti-function
timers,
Operation,
MODULATOR--device
HSYNC
and
into
Main
which
a
typeinput,andalsomodulatesthissignal,combinedwith
a¡r
audio,
onto
device
by a
processing for
Interrupts
if they
There
VSYNC
then
Level
proprietary
Theory
of operation,
details.
Dígital
instrunents
such
for
connunications
6B50
74LSO5,
Peripheral,
usART
for
System.
combines
conposite
RF camier
the
for
naskable
are
are
not
do
three
priorities: the
interrupts'
signaled
are
inputs
Glue.
and
MFP,
chfp
Interface.
comnunication.
chip,
PC-900
and
68901.
atso
RS232
connunicatÍon.
video signals
s:'.gnal
for
for
output
processor
to
the device.
in software,
and
to
systen
current
lowest
the
see
ha¡rdles
meet the
(IPL0-2).
which
Main
An electrical
comnunicate.
In
driver
photocoupler),
Interrupt
see
R,G,B'
nonitors
a
to
requiring
television.
stop
It is a
priority
highest
are
cPU
Theory
all
a¡¡d
standard
AIso,
the
receiver
and
and
control,
Theory
VSYNC,
it
h¡hat
type
neaning
are
HSYNC
the
on
of
RAM
video
the
1040ST,
MFP
an
of
and
this
PHASE
LOCKED
onto
on
unstable,
may
shield
shield,
printed
PSG--Progranmable
Genéral
three
Rs232c--Electical
the
using
MFP,
Mega Service
LQOP--circuit
color
the
T.V.
the
on
be
or
or
circuit
Instn¡ments
sound
physical
this
PSG,
Manual
which
burst
lrJithout
flickeríng
a daughter
hand
reference
this
or shiftÍng
board
wired
onto
(possibly) in later
board.
Sound
channels.
standard
and
standarã.
1488,
Generator,
AY-3-8910.
used
for serial
logical
In the
1489 cniPs.
and
device
9.2
locks
frequency
circuit,
located
naÍn board
the
versions,
also
parallel
in
which
ST
horizontal
the
for accurate
the
on
front
on the
colors
about
in
within
integrated
YM2149.
Has two I
Uit
port
digital
comnunication.
perforns
computers,
sync
T.V.
screen.
of
Yanaha
I/0
audio.
and
comnunication
consists
signal
color
become
PPL
The
video
the
video
the
version
into
the
of
ports and
AIso
the
of
Glossary

L772--Western
Digital
Fl-oppy
Disk
Controller.
6850--atso
rnterfaces
communication
keyboard
6890t--see
SUPERVTSOR
alr
MFP.
MoDE--state
hardware
instructions.
Register.
and
switches
apprication
mode
if
usER
MoDE--state
areas
privilege
SUPERVISOR
vsYNC--signal
device.
l¡M2149--see
PSG.
(Asynchronous
AcrA
between
bus.
conmunication,
of
a¡rd RAM locations,
Deternined
The
operating
to
(although
it
wishes).
of
the cPU in
in
the memory
violatÍon
MODE.
used for
Occurs
aE
70
connunication
B
In
the
and
the cPU
by the
system
user mode
the
nap
exception
vertical
(monochrome),
Hz
pararlel
bit
ST,
there
one for
in
which it is
operates
before
application
which
are
disallowed
if
are thro
MIDI
perform
and
state
of a bit in
passing
ca¡r
certain instructions
attempted).
synchronization
or
rnterface
bus
Adapter).
and
6850s,
conmunication.
arlowed
sone
to
priviriged
the
in
supervisor
control
enter
supervisor
(resulting
See
of cRT
or 60 Hz
50
serial
one for
access
status
node,
to
in
also
display
color.
an
a¡rd
a
Mega
Service
Manual
9.3
Glossary
