Atari 800 XL ROSE User manual

SERVICE MANUAL
FOR THE
ATARI 800XL 'COMPUTER

SERVICE MANUAL
FOR THE
ATARI 800XL COMPUTER
Electronic Dimsnsions Post Office Box 1846 San Luis Obispo California 93406 USA

All of the information contained In this manual is believed to bo accurate and reliable. However,
no responsibility shall be assumed for any consequences arising out of the use of this material.
Atari and 800XL are registered trademarks of Atari, Inc.
Reproduction of this manual in any form is prohibited.
3

TABLE Q£_ CONTENTS
SECTION 1- THEORY OF OPERATION
User Interface
Mechanical Theory
Electrical Theory
6502C CPU Microprocessor
Alphanumeric Television InterfaceController (ANTIC)
Graphic Television Interface Adaptor (GTIA)
POT KEYboard Integrated Circuit (POKEY)
Peripheral Interface Adapter (PIA)
Memory (ROMs and DRAMs)
Memory Management Unity (MMU)
Operating System ROM
RF Modulator
Monitor Output
Power Supply
System Interface
Serial Input/Output (SIO) Interface
Controller Jade Interfaces
Parallel Bus Interface (PBI
)
Cartridge Interface
Keyboard Interface
SECTION 2-SELF TESTING
Overview
Equipment Needed
Self Test Features
Description of Self Tests
Memory Test
Audio Yisual Test
Keyboard Test
All Tests
SECTION 1-DISASSEMBLY/ASSEMBLY
SECTION 4-TROUBLESHOOTING
AGuide to Aid in the Rapid Diagnosis of Problems
SECTION 5- SCHEMATIC AND PARTS LIST
Parts List
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A

SECTION I
THEORY OF OPERATION
The Atari 800XLWIs 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/120QXLMComputers.
The printed circuit board contains 64K of RAM ,an operating systems that contains ore 16K X8
ROM and an on-board Atari BASIC programming language I.C. The console contains the keyboard
and four function keys (including aHELP key), plus aRESET key, adetachable (RF) TV interface
cable, connector Jack for daisy-chaining peripherals and connecting hand controllers, asingle
cartridge slot, ore status LED (POWER), a5 pin DIN Monitor Jack, and aparallel bus interface
USER INTERFACE
The Atari 800XL is ageneral purpose microcomputer that uses a6502C 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 a3/4 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 aprogram. 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
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Self-Test menu appears.
RESET -Interrupts aid restarts the operating system (OS) or cartridge. When pressed while
the computer is ON, this key enables the BASIC.
SELECT -Selects different program or game variations.
START -Starts the gone or program.
6

To Cartridge To Joysticks, Paddles, Etc.
System Block Diagram
7

MECHANICAL THFORV
The 800XL computer console contains asingle motherboard which houses all the chips of the
system and provides connectors for interfacing external modules to the console. It includes the
CPU,RAM ,OS and BASIC ROM's. The motherboard uses acommon address bus, data bus aid clock
lines. The sixteen-line address bus allows the microprocessor to directly address 64K memory
locations. The eight- line data bus provides the communication and data path between the
functional modules. The power is provided by an external power supply and routed throughout
the console
The keyboard is the user interface with the computer.
The keyboard connects to the PC Board by a24-connector ribbon cable.
All peripherals connect to the 800XL either through the SIO connector or the PBI. Power enters
through the 7-Pin DIN connector on the rear panel. Power On/Off is controlled by the ON/OFF
switch on the rear panel. RF to the TV switchbox arrives from an RCA phonoconnector and RF
cable. Composite Video composite luminance, and audio signals to the monitor arrive from a5
pin DIN monitor jack on the reer panel.
ELECTRICAL THFORV
DIGITAL HARDWARE
The digital hardware consists of:
*The 6502C CPU microprocessor
*The Alphanumeric Television Interface Controller (ANTIC)
*The Graphics Television Interface Adaptor (GTIA)
*The POT KEYboard Intecrated Circuit (POKEY)
*The Peripheral Interface Adaptor (PIA)
*The Memory (Operating System ROM ,64K RAM ,Atari BASIC ROM ,Rev. B)
*Miscellaneous Logic
Memory Management Unit (MMU)
Delay Line
*Parallel Bus Interface (PBI
)
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6.502C CPU Microprocessor
The 6502C CPU microprocessor contains register flags, interconnections, arithmetic logic,
control logic, and all recognized operation codes. The characteristics of the microprocessor
include:
*Byte-oriented structure
*Decimal and binary arithmetic modes
*Integral clock circuit
*Seven addressing modes
*Single +5 volt DC power requirement
*Stack pointer
*Two interrupt levels
*151 opcodes
*64K address range
*True Indexing
Ground VSS
Ready Input RDY
Phase 1Clock FPH1
Interrupt Request IRQ
NC
Non Maskable Input NMI
+5V Power NC
VCC
Address Bus AO
Address Bus A1
Address Bus A2
Address Bus A3
Address Bus A4
Address Bus A5
Address Bus A6
Address Bus A7
Address Bus A8
Address Bus A9
Address Bus A10
Address Bus All
V/
1•40
239
338
437
536
635
734
833
932
10 31
11 30
12 29
13 28
14 27
15 26
16 25
17 24
18 23
19 22
20 21
kti> Reset
FPH2 Phase 2Clock
SO Set Overflow
FPHO Phase 0Clock (in)
R/¥ Read/Write
MT HALT Input
NC
DO Data Bus
D1 Data Bus
D2 Data Bus
D3 Data Bus
D4 Data Bus
D5 Data Bus
D6 Data Bus
D7 Data Bus
A15 Address Bus
A14 Address Bus
A13 Address Bus
A12 Address Bus
VSS Ground
6502C (Modified)
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Alphanumeric Television Interface Controlter fANTirt
The ANTIC Display Processor is acustom display microprocessor with an instruction set
customized for graphics generation. It also has the ability to control the ADDRESS &DATA bus
and RAM Refresh.
Ground VSS
Alphanumeric Data MT
Alphanumeric Data ANl
Light Pen IF
Alphanumeric Data MT
System Reset FPU
Interrupt Output NM1
Refresh FFF
HALT TOUT
Address Bus A3
Address Bus A2
Address Bus A1
Address Bus AO
Read/Write R/TT
Ready Output RDY
Address Bus A10
Address Bus A12
Address Bus A13
Address Bus A14
Address Bus A15
D4 Data Bus
D5 Data Bus
D6 Data Bus
D7 Data Bus
RST Reset
F0O Fast Phase 0Clock
00 Phase 0Clock
D3 Data Bus
D2 Data Bus
D1 Data Bus
DO Data Bus
02 Phase 2Clock
A4 Address Bus
A5 Address Bus
A6 Address Bus
A7 Address Bus
A8 Address Bus
A9 Address Bus
All Address Bus
VCC +5V Power
ANTIC

Graphic Television Interface Adaptor (GTIA)
The GTIA interfaces with the ANTIC processor on one side and with the video summation circuitry
on the other. Its primary task is to generate color and luminance signals from the bit stream it
receives from the ANTIC Display Processor. It also processes the Function keys, provides the
keyboard “beep" via the TV speaker and monitors controller Trigger lines.
Address Bus A1 1•
Address Bus A$ 2
Ground VSS 3
Data Bus D3 4
Data Bus D2 5
Data Bus D1 6
Data Bus DO 7
Trigger 0T0 8
Trigger 1T1 9
Trigger 2T2 10
Trigger 3T3 11
Option S0 12
Start SI 13
Select S2 14
Keyboard Click S3 15
PAL Color Delay PAL 16
Color Delay CADd 17
Alphanum. Data 0AN0 18
Alphanum. Data 1AN1 19
Alphanum. Data 2AN2 20
40 A2 Address Bus
39 A3 Address Bus
38 A4 Address Bus
37 D4 Data Bus
36 D5 Data Bus
35 D6 Data Bus
34 D7 Data Bus
33 R/¥ Read/Write
32 US' Chip Select 1
31 LUM 3Luminance Line
30 02 Phase 2Input
29 F0O Clock Out
28 OSC Oscillator Input
27 VCC Power
26 TOUT HALT
25 CSYNC Output Sync.
24 LUM 2Luminance 2Output
23 LUM 1Luminance 1Output
22 |
LUM 0Luminance 0Output
21 !COL Color
GTIA
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PQT KEYboard Integrated Circuit (POKEY)
The POKEY is acustom Large Scale Integrated circuit (LSI )chip, it is used for audio generation
,
Serial Input/Output (SIO) Data and Clocks, POT Controller interface scan, and keyboard scan.
Ground VSS 1•40 D2
Data Bus D3 239 D1
Data Bus D4 338 D0
Data Bus D5 437 AUDIO
Data Bus D6 536 A0
Data Bus D7 635 A1
Phase 2Clock 02 734 A2
Pot Scan P6 833 A3
Pot Scan P7 932 R/¥
Pot Scan P4 10 31
Pot Scan P5 11 30
Pot Scan P2 12 29 TEH
Pot Scan P3 13 28 SOD
Pot Scan P0 14 27 ACLK
Pot Scan PI 15 26 BCLK
Keyboard Response EE7 16 25 KR1
+5V Power VCC 17 24 SID
Keyboard Scan Y5 18 23 w
Keyboard Scan W19 22 K1
Keyboard Scan YJ 20 21 YZ
Data Bus
Data Bus
Data Bus
Audio Out
Address Bus
Address Bus
Address Bus
Address Bus
Read/Write
Chip Select
Chip Select
Interrupt Request
Serial Output Data
Serial Output Clock
Bidirectional Clock
Keyboard Response
Serial Input Data
Keyboard Scan
Keyboard Scan
Keyboard Scan
POKEY
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Peripheral Interface Arlantnr (PIA1
The PIA is ageneral purpose Input/Output (I/O) chip. It monitors the X-Y controller interfaces
and the SIO control lines. In certain applications it may control the MMU logic.
Ground VSS 1•40
Controller Input PAp 239
Controller Input PA1 338
Controller Input PA2 437
Controller Input PA3 536
Controller Input PA4 635
Controller Input PA5 734
Controller Input PA6 833
Controller Input PA7 932
Enable/Disable Output PBd 10 31
Not Used PB1 11 30
Output to LED 1PB2 12 29
Not Used PB3 13 28
Not Used PB4 14 27
Not Used PB5 15 26
Not Used PB6 16 25
Self Test Output PB7 17 24
Control Line CB1 18 23
Command Output CB2 19 22
+5V Supply Voltage VCC 20 21
CA1 Control Line
CA2 Motor Control Output
TKQK Interrupt Request (Out)
wInterrupt Request (Out)
A1 Address Line
A0Address Line
W5FT Reset Input
DO Data Line
D1 Data Line
D2 Data Line
D3 Data Line
D4 Data Line
D5 Data Line
D6 Data Line
D7 Data Line
02 Clock Input
CS1 Chip Select Input
Z52 Chip Select Input
CS0 Chip Select Clock Input
R/¥ Read/Write
PIA
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MEMORY (ROMS AND DRAMS)
BASIC RQM
The Atari 800XL has built-in Atari BASIC (Rev. B) residing in an 8K X8ROM. This is
equivalent to having an Atari BASIC cartridge permanently plugged into the console. Any
cartridge plugged into the computer takes precedence over the built-in BASIC.
DRAMS
The 800XL Dynamic Random Access Memories (DRAMS) consist of eight 64K XIDRAMS.
MEMORY MANAGEMENT UNIT (MMUl
The memory management unit (MMU) address decoding circuitry consists of aPLA
(Programmable Logic Array) I.C. ,one 3to 8decoder and afew gates. The input to the circuitry
includes the address lines A8 through A15as well ss control signals, such as ROM enable (from
PIA) and DRAM refresh from ANTIC. Some of the most important outputs of this circuitry
include select signals for the 0TIA, POKEY, PIA, OS ROM ,DRAMS, BASIC and cartridge.
Q.5. RQM
The 800XL operating system is resident in one 16K X8ROM. The ROM address inputs are from
CPU address lines AO through A1 3. The chip selects from the address decoding circuitry and
generates data on CPU data lines DO through D7. The ROM requires apower input of +5 volts.
RF MODULATOR
The RF modulator accepts the composite video from the video summation circuitry and the
mono-aural audio signals and produces amodulated signal suitable for the television.
With a75 Ohm termination, the modulated signal has the following characteristics:
Maximum Voltage: 2mV
Minimum Voltage: ImV
Audio Sound Carrier Frequency: 4.5 MH2
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Frequency Response:
Channel 2-
Band: 6MHz
Video Carrier: 55.25 MHz
Audio Carrier: 59.75 MHz
Channel 3-
Band: 6MHz
Video Carrier: 61.25 MHz
Audio Carrier: 65.75 MHz
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MONITOR OUTPUT
The 5pin DIN monitor output jack (J2) accepts the composite video and the composite
luminance signals from the OTIA video summation circuitry and the amplified mono-aural audio
signals from POKEY. J2 then transfers these signals directly to the input of the video monitor
via a5pin DIN monitor cable.
The output signals have the following characteristics:
Min. Voltage
Composite Yideo 750 mV P-P
Composite Luminance I.2Y P-P
Audio 600 mV P-P
Max. Voltage
1VP-P
1.5V P-P
750 mY P-P
POWER SUPPI Y
The power supply connector is a7-pin DIN connector.
The Atari 800XL has an external power supply that accepts 110 VAC (nominal )from the power
lines and provides +5 YDC output (+/- 2%). The maximum rating for the supply is +5 volts
and 1.2 amps.
Power Supply Connector Pin Assignments
(Looking Toward Computer)
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SYSTEM INTERFACE
The 800XL provides the following interfaces:
*Serial input/output (SIO)
*Controller Jacks
*Parallel Bus Interface (PBI)
*Cartridge Interface
*Keyboard Interface
SERIAL INPUT/OUTPUT (SIQ) INTERFACE
The Atari 800XL communicates with peripheral devices via an asynchronous serial port (19.2K
Baud rate max.), Data is transmitted and received as eight bits of serial data. LSB is sent first
precededby alogic zero start bit and succeeded by alogic one stop bit The serial data out is
transmitted or received as positive logic. The serial data out line always assumes its new state
when the serial clock out line goes high. Clock out goes low in the center of data ait.
The bus protocol specifies that all commands must originate from the computer and that
peripherals present data on the bus only when commanded to do so. Every bus operation goes to
completion before another bus operation is initiated. An error detected kany point in the bus
operation aborts the entire sequence. Abus operation consists of the following elements:
-Command Frame (From Computer)
-Command Frame
1) Data Send
2) Date Receive
3) Immediate (No Data-Command Only, i.e., status)
-Acknowledge Frame (From Peripheral)
-Optional Data Frame (To Or From Computer)
-Complete Frame (From Peripheral)
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1) Clock Input
2) Clock Output
3) Data Input
4) Ground
5) Data Output
6) Ground
7) Command
8) Motor Control
9) Proceed
10) +5V/Ready
11) Audio Input
12) Not Connected
13) Interrupt
SIO Connector Pin Assignments
CONTROLLER JACK INTERFAX
The 800XL provides two controller jack interfaces. Both are functionally and electrically
identical. The controller jacks are 9-pin D-type male connectors.
1) Joystick Forward Input
2) Joystick Backward Input
3) Joystick Left Input
4) Joystick Right Input
5) BPotentiometer Input
6) Trigger Input
7) +5 Volts
8) Ground
9) APotentiometer Input
Controller Jack Pin Assignments
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PARALLEL BUS INITFPPAPF
The parallel bus Interface (PBI )provides an unbuffered, direct connection to the address data
aid control signals shown below. It could be used to interface peripherals, parallel bus devices
and external applications.
Ground GND 12EXTSEL External Select
Address Output A0 34A1 Address Output
Address Output A2 56A3 Address Output
Address Output A4 78A5 Address Output
Address Output A6 910 GND Ground
Address Output A7 11 12 A8 Address Output
Address Output A9 13 14 A10 Address Output
Address Output All 15 16 A12 Address Output
Address Output A13 17 18 A14 Address Output
Ground GND 19 20 A15 Address Output
Data Bi-Directional D0 21 22 D1 Data Bi-Directional
Data Bi-Directional D2 23 24 D3 Data Bi-Directional
Data Bi-Directional D4 25 26 D5 Data Bi-Directional
Data Bi-Directional D6 o. 27
o28 g
|
D7 Data Bi-Directional
Ground GND 29 30 sGND Ground
Phase 2Clock Output B02. 31 GQ
32 GND Ground
Reserved NC 33 34 RST Reset Output
Interrupt Request Input IRQ 35 36 RDY Ready Input
Reserved NC 37 38 EXTENB External Decoder Output
Reserved NC 39 40 REF Refresh Output
Column Address Output CAS 41 42 GND Ground
Math Pack Disable Input MPD 43 44 RAS Row Address Strobe Output
Ground GND 45 46 LR/W Latcher Read/Write Output
Reserved NC 47 48 NC Reserved
Audio Input AUDIO 49 50 GND Ground
PBI Connector Pin Assignments
(Looking Into Computer)
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