*********
Welcome to Project 64!
The goal of Project 64 is to preserve Commodore 64 related documents
in electronic text format that might otherwise cease to exist with the
rapid advancement of computer technology and declining interest in 8-
bit computers on the part of the general population. If you would like
to help by converting C64 related hardcopy documents to electronic
texts please contact the manager of Project 64, Cris Berneburg, at
74171.2136@compuserve.com.
Extensive efforts were made to preserve the contents of the original
document. However, certain portions, such as diagrams, program
listings, and indexes may have been either altered or sacrificed due
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for these limitations, alterations, and possible omissions.
Document names are limited to the 8.3 file convention of DOS. The
first characters of the file name are an abbreviation of the original
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The author(s) of the original document and members of Project 64 make
no representations about the accuracy or suitability of this material
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warantee of the original document, if any, that may included in this
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*********
The Project 64 etext of the Commodore 64 Service Manual, converted to
etext by Sami Rautiainen <a94ssara@kotakk.fi>. This is a "mostly
complete" manual, version 0.9 (Jan 1997). Hypertext version can be
found from URL http://www.kotakk.fi/~a94ssara/.
C64SM09.TXT, February 1997, etext #165.
This manual is formatted with 50 lines per page. Each page break is
identified with a tilde (~) character. There are some pages that did
not fit on the 50 lines; those pages are broken into two (or more) 50
line sections. [Normally Project 64 documents are not formatted to a
particular page format other than being no more than 71 columns wide.]
Most of the figures was too complex to convert to ASCII and are
identified as [Figure: Blah blah].
Still to do: a few pin assignments.
Visit Project 64 homepage at URL ...
http://ourworld.compuserve.com/homepages/pcgeek/proj64.htm
or p64nf.htm for no frames.
*********
~
SERVICE MANUAL
MODEL C64 COMPUTER
September 1985 PN-314001-02
Commodore Business Machines, Inc.
1200 Wilson Drive, West Chester, Pennsylvania 19380 U.S.A.
Commodore makes no expressed or implied
warranties with regard to the information
contained herein. The information is made
available solely on as is basis, and the
entire risk as to quality and accuracy is
within the user. Commodore shall not be liable
for any consequential or incidental damages in
connection with the use of the information
contained herein. The listing of any available
replacement part herein does not constitute in
any case a recommendation, warranty or guaranty
as to quality or suitability of such replacement
part. Reproduction or use without expressed
permission, of editorial or pictorial content,
in any matter is prophibited.
This manual contains copyrighted and proprietary information. No part of
this publication may be reproduced, stored in a retrival system, or
transimitted in any form by any means, electronic, mechanical,
photocopying, recording or otherwise, without the prior written
permission of Commodore Electronics Limited.
Copyright (C) 1985 by Commodore Electronics Limited.
All rights reserved.
~
CONTENTS
Page
SPECIFICATIONS .................................................. 1
PRODUCT PARTS LIST .............................................. 2
BLOCK DIAGRAM ................................................... 3
CIRCUIT THEORY
POWER SUPPLY ................................................ 4
RESET LOGIC ................................................. 5
CLOCK CIRCUITS .............................................. 6
I/O, RAM, EXPANSION LOGIC ................................... 7
RAM CONTROL LOGIC ........................................... 8
5 PIN VIDEO AND AUDIO OUTPUTS ............................... 9
8 PIN VIDEO AND AUDIO OUTPUTS ............................... 10
CASSETTE INTERFACE .......................................... 11
KEYBOARD, JOYSTICK & PADDLE INTERFACES ...................... 12
SERIAL INTERFACE, USER PORT ................................. 13
TROUBLESHOOTING GUIDE ........................................... 14
BOARD IDENTIFICATION ............................................ 17
PCB ASSEMBLY #326298-01
BOARD LAYOUT ................................................ 18
PARTS LISTS ................................................. 19,20
SCHEMATIC #326106 ........................................... 21,22
PCB ASSEMBLY #260407-04
BOARD LAYOUT ................................................ 23
PARTS LIST .................................................. 24,25
MODULATOR SCHEMATIC #251025 ................................. 26
SCHEMATIC #251138 ........................................... 26,27
PCB ASSEMBLY #250425-01
BOARD LAYOUT ................................................ 28
PARTS LIST .................................................. 29,30
MODULATOR SCHEMATIC #251696 ................................. 31
SCHEMATIC #251469 ........................................... 31,32
PIN ASSIGNMENTS ............................................. 33
~
C64 COMPUTER
General description
The "All Purpose" Commodore 64 us the complete computer for
education, home or small business applications. Supported
by quality peripherals and a full range of software, the
Commodore 64 is perfect for the family. No other computer
can offer such variety of uses and applications at such an
affordable price.
Memory 64K RAM
ROM 20K ROM Standard (includes operating system and BASIC
interpreter)
Microprocessor 6510A Microprocessor - 1.02 MHz clock
Compatible with the 6502
Display 40 Columns X 25 lines of text
Colors 16 Background, border and character colors
Characters Upper & lower case letters, numerals and symbols
Reverse characters
All PET graphic characters
Display modes Text characters * High resolution graphics
Resolution 320 X 200 Pixels
Sprites 8 independent sprites
Each consists of 24 X 21 pixels and up to 4 colors
Each independently expandable horizontally and vertically
Collision detection for sprite to sprite and data to sprite
collisions
Sound 6581 Sound Interface Device includes 3 independent tone
generators - each with 9 octaves
Each voice includes programmable ADSR generator (Attack, Decay,
Sustain, Release) and control of sawtooth, triangle, square,
variable pulse and noise waveforms
Full filtering capabilities with low, high and band pass
filters
External sound input
Keyboard Full size typewriter style design
~
Keys 66 Keys total
2 Cursor control keys
4 Function keys (up to 8 user defined/programmable functions
possible)
Upper and lower case character set
Graphic character set
Inputs/Outputs User port
Serial port
ROM cartridge port
2 Joystick/paddle ports
Video port C1530 Cassette drive interface port
Features Built-in BASIC 2.0 - over 70 commands, statements and functions
Full screen editor
Peripherals C1541 Disk drive
C1530 Datasette
MPS 801 Dot matrix printer
MPS 802 Dot matrix printer
MPS 803 Dot matrix printer
DPS 1101 Daisey wheel printer
C1520 Plotter/Printer
C1702 Color monitor
CM141 Color monitor
Power requirements
120 Volts, 60 Hz
Specifications subject to change without notice.
1
~
PARTS LIST C-64
PLEASE NOTE: Commodore part numbers are prived for reference only and do
not indicate the availability of parts from Commodore. Industry standard
parts (Resistors, Capacitors, Connectors) should be secured locally.
Approved cross-references for TTL-chips, Transistors, etc. will be
available in manual form through the Service Department in November of
1984. Unique or non-standard part will be stocked by Commodore and are
idicated on the parts list by a "C".
TOP CASE ASSY
Top Case C 326113-01
Keyboard C 326166-02
LED Plate C 326160-01
Nameplate C 326161-01
Lamp Hold Set C 903820-03
LED Assembly C 1001039-01
BOTTOM CASE ASSY
Bottom Case C 326114-01
Foot, Self-Adhensive C 950157-04
PCB Shield Plate C 326131-01
PCB Insulation Sheet C 326288-01
ACCESSORIES
Users Manual C 326114-01
Power Supply C 950157-04
RF Cable C 326131-01
Switch Box C 326288-01
2
~
[Figure: C-64 Block Diagram]
3
~
C64 CIRCUIT THEORY
+-------------------------------------------------------------------------+
| There are three versions of the C64. The C64 with five pine connector |
| video output (326106). The C64 with an eight pin connector video output |
| (251138), and the C64B which has improved system clock circuit design |
| (251469). Most circuit theory explanations will be the same for all |
| three versions. Refer to schematic 326106 unless noted otherwise. |
+-------------------------------------------------------------------------+
The Power Supply
The external power supply generates a regulated 5VDC and 9VAC. 5VDC is applied
to pins 5 and 1 of CN7 on the C64 pcb. Filtered by L5, C97, and C100 it is then
controlled by on/off switch S1. This 5VDC output supplies the microprocessor
logic.
9VAC is applied to pins 6 and 7 of CN7 on the C64 pcb. +12VDC, +5VDC CAN and
9VAC unregulated are outputs that are derived from this 9VAC supply. The 9VAC
supply is made available on pins 10 and 11 of the USER PORT CN2.
12VDC Generation
9VAC is added to 9VDC through CR6, and rectified by CR5. The unregulated DC
output is filtered by C88 and C89 then regulated at 12VDC by VR1. The regulated
output is filtered by C57 and C59. The 12VDC supplies the VIC and SID IC, and
the audio amplifiers.
+5VDC CAN Generation
9VAC is rectified by CR4. The unregulated DC output is filtered by C19, and C95
then regulated at 5VDC by VR2. The regulated output is filtered by C102 and
C103. The output called 5VDC CAN is sperated and individually filtered into two
outputs called Vvid and Vc. Vvid is the 5VDC supply for video circuits, and Vc
is the 5VDC supply for the clock circuits.
9VDC Unregulated Generation
CR4 rectifies the 9VAC input. The output is 9VDC unregulated. This supply powers
the cassette motor transistor amplifier circuits, and the RF modulator on the
C64B version.
[Figure: Power Supply Circuits] 4
~
C64 CIRCUIT THEORY
[Figure: Reset Circuit schematic]
Reset Logic Circuits
U20 is a 556 timer configured as a one shot multivibrator. The output pulse
width is determined by the size of R34 and C24. Pulse width = 1.1 x R34 x
C24 = .5 seconds. The output on pin 9 is "high" active. The output of U8 is
"low" active. Reset initializes all the processor logic and causes the
processor to load the program counter register with the address og the
first instruction of the operating sysstem program called the KERNAL. The
starting address is stored in locations $FFFC and $FFFD. The first
instruction is decode and executed giving KERNAL control of the computer
operations. The reset pulse occurs when turning the power on to the
computer.
5
~
C64 CIRCUIT THEORY
[Figure: Clock circuit schematic]
The C64 Clock Circuits.
Crystal Y1 develops a 14.31818MHz fundamental frequency clock signal. U31
is a Dual Voltage Controlled Oscillator. The ouput on pin 10 is a 14.31818
MHz clock signal called the color clock. R27 can be adjusted to obtain
exact ouput frequency. U30 is a frequency divider that ouputs a 2MHz signal
on pin 6. U29 is a D flip flop which ouputs a 1MHz signal on pin 9. U32 is
a Phase/Frequency Detector which compares the ouput of the U29 to the phase
0 clock, and ouputs a dc voltage on pin 8 that is proportional to the phase
diffrence between the inputs. Thes second half of the Dual Voltage
Controller Oscillator U31 generates an 8.1818MHz clock signal called the
DOT Clock. The VIC IC divides the DOT clock by eight and ouputs this as the
phase 0 clock on pin 17. The output of the Phase/Frequency Detector is
applied to the frequency control input pin 2 of U31. This causes tracking
of the dot clock and the color clock because one input, pin 4 of U32, is
the phase 0 clock which is derived from the dot clock, and the other pin 1
of U32, is derived from the color clock.
[Figure: Clock circuit (C64B) schematic]
The C64B Clock Circuits. Refer to schematic 251469
Crystal Y1 develops the fundamental 16Mhz clock signal. U31 is a Clock
Generator IC that outputs the 8.1818MHz DOT clock on pin 6, and the
14.31818 MHz color clock on pin 8.
6
~
C64 CIRCUIT THEORY
[Figure: I/O, ROM and expansion port schematic]
I/O and ROM Address Decoding and Expansion Port.
I/O Address Decoding Logic
U17 is a Programable logic array (PLA). The output F5 on pin 12 called I/O
goes "low" when any of the I/O devices controlled by U15 are selected. The
addresses are listed below for each device.
VIC IC $D000 - $D02E
SID IC $D400 - $D7FF
Color Ram $D800 - $DBFF
CIA 1 $DC00 - $DC0F
CIA 2 $DD00 - $DD0F
I/O 1 $DE00 - $DEFF
I/O 2 $DF00 - $DFFF
ROM Address Decoding.
Basic ROM resides at locations $A000 - $BFFF. The output F1 pin 17 of the
PLA U17 goes "low" when the BASIC ROM is selected. The KERNAL ROM resides
at locations $E000 - $FFFF. The output F2 pin 16 of the PLA U17 goes "low"
when the KERNAL ROM is selected. The CHARACTER GENERATOR ROM resides at
locations $D000 - $DFFFF. The output F3 pin 15 of the PLA U17 goes "low"
when the Character Generator ROM is selected.
The Expansion Port Connections.
The expansion port is an extension of the microprocessor address, data, and
control bus. ROML decodes addresses $8000 - $9FFF, and ROMH decodes
addresses $E000 - $FFFF. These are outputs from the PLA used to select the
catridge inserted in the expansion port. I/O 1 input from U15 decodes
addresses $DE00 - $DEFF. I/O 2 output from U15 decodes addresses $DF00 -
$DFFF.
7
~
C64 CIRCUIT THEORY
[Figure: RAM control logic schematic]
RAM Control Logic.
U13 and U25 are multiplexers. The address output from the microprocessor
are passed to RAM via U13 and U25 when the ouput Address Enable Control
(AEC) from the VIC IC is "high". When AEC is "low" the VIC IC ouputs
refresh addresses on pins 24 - 31. AEC goes "low" when the system clock,
phase 2, is "low". Since all I/O decoding occurs when phase 2 is "high",
refresh is transparent to the processor.
Eight 4164 DRAMS provide 64k bytes of memory. One 2114 RAM (U6) provides
512 bytes of memory allocated for screen color data storage.
8
~
C64 CIRCUIT THEORY
[Figure: 5 pin video and audio schematic]
5 Pin Video and Audio Output Circuits
Pin 15 of the VIC IC is the sync/luminance output. Pin 14 is the color
output. A composite video output is created by mixing sync/luminance and
color. The composite output is applied to the RF modulator, and also passed
to the monitor connector CN5 on pin 4. The color output is not made
available on the monitor connector CN5 as on the 8 pin version, and the RF
modulator mixes audio with the composite video producting the TV RF output,
unlike the 8 pin version RF modulator which creates the composite video
output.
9
~
C64 CIRCUIT THEORY
[Figure: 8 pin video and audio schematic]
8 Pin Video and Audio Output Circuits. Refer to schematic 21469
U19 is the Video Interface Chip (VIC). Sync (horizontal and vertical), and
luminance (video) is output on pin 15. This signal is passed to pin 2 of
the RF modulator. Color is output on pin 14, and passed to pin 3 of the
modulator. Light pen inputs are sensed by the VIC IC on pin 9. U18 is the
Sound Interface Device (SID). The audio output is on pin 27, and audio
input is on pin 26. The RF modulator mixes sync/luminance, color, and audio
out, generating a TV composite signal on pin 5. The RF modulator also
passes the VIC outputs to the monitor connector CN5. Audio out on pin 27 is
amplified by Q2, and output on pin 3 of CN5. Audio in is applied to pin 5
of CN5, then to pin 26 of the SID IC. Inputs from paddles connected to on
of the control ports are monitored by the SID IC on pins 23 and 24.
10
~
C64 CIRCUIT THEORY
[Figure: Cassette interface schematic]
The Cassette Interface Circuits.
U7 is a 6510 microprocessor. One of the features of the 6510 is a built in
parallel I/O port (P0-P5). P3 - P5 control most of the cassette interface
circuitry. P3 pin p6 of U7 outputs the write data signal to connector CN3
on pins E and 5. P4 is an input tha senses the play switch depressed on the
cassette devk. P5 is on output that controls the cassette motor. When P5
goes "low", Q2 cuts off, CR2 regulates Vb of Q1 at 7.5 volts, this forward
biases Q1 and Q3, passing current through the cassette motor coil. U1 is a
Complex Interface Adapter (CIA). Parallel ports, serial outputs, and Timers
are standard features of the CIA. Read data enters on pins D, 4 of CN3. U1
accepts the read data signal on the FLAG input pin 24.
11
~
C64 CIRCUIT THEORY
[Figure: Interface control schematic]
Keyboard, Joystick, and Padle Interface Circuits.
Keyboard Interface
U1 is a Complex Interface Adapter (CIA). Both parallel ports are used to
decode the keyswitches on the keyboard. Parallel port A signals (PA0 - PA7)
are outputs. PArallel port B signals (PB0 - PB7) are inputs. A "0" bin is
shifted through the parallel port A, when a key is depressed ont the
keyboard the "0" bit is returned on one of the parallel port B inputs. A
program in the KERNAL ROM generates the shifting "0" bit output on parallel
port A, and decodes the signals returning on the parallel port B inputs.
Depressing the restor key causes U20 to trigger. U9 pin 6 goes "low"
generating a Non- Maskable Interrupt (NMI) at the processor. This causes
the processor to execute a subroutine which initializes the I/O interfaces.
If the STOP key is depressed at the same time, BASIC flags are initialized.
[Figure: Keyboard matrix]
Joystick Interface
U1 also controls the joystick. Parallel port A accepts inputs from the B
joystick connected to control port 2. Parallel port B accepts inputs from
the A joystick connected to control port 1. When the joystick is moved up,
down, left, right, or the fire button is depressed, a ground potential is
applied to the appropriate input of U1.
Paddle Interface
A Variable resistor is connected to adjusting knob on the paddle. When the
konb is rotated, the resistance varies controlling the time constant of an
RC network. The Voltage developed across the capacitor is input to an A/D
converter internal to the SID chip U18. The digital output is stored in one
of the SID registers. The paddle position can be determined by the reading
the contents of the appropriate register. U28 is a 4066 CMOS switch. The
signals from the paddles are passed to the SID chip when the Enable inputs
(E0 - E3) of U28 are "high".
NOTE: U1 port assgnments are incorrect on schematics. Refer to Keyboard
Matrix for correct assignments.
12
~
C64 CIRCUIT THEORY
[Figure: Serial interface schematic]
The Serial Interface and User Port Circuits
The Serial Interface.
U2 is a Complex Interface Adapter (CIA). Parallel port signals PA3-PA7
control the serial bus inrface. PA3 is the Attention (ATN) output. This
signal is inverted by U8 before being transmitted to a device on the bus.
PA4 is the clock output. Data transmitted from the C64 to a device on the
bus is synchronized by this clock signal. U8 inverts the output PA4. PA5 is
the data output. U8 inverts this output also. Data ransmitted from a device
on the bus to the C64 is synchronized by a clock generated by the
transmitting device. The Clock signal is input on PA6. Data transmitted
from a device on the bus to the C64 is input on PA7. When a device on the
bus wants to communicate with the C64, SQR IN goes "low" indicating service
is requested.
The User Port
Parallel port B of U2 (PB0 - PB7) is made avalable on the user port.
Parallel data transfers with external device are made very easily through
this parallel port. SP2 and SP1 are bi-directional serial ports. CNT1 and
CNT2 are bi-directional synchronizing clock signals for each serial bus.
13
~
64 TROUBLESHOOTING GUIDE
+--------------------------------------+------------------------------------+
| SYMPTOM | POSSIBLE SOLUTION |
+--------------------------------------+------------------------------------+
|Blank screen on power up. |Check External Power Supply |
| | U4 (KERNAL ROM), U17 (PLA) |
| | U7 (6510 MPU), U3 (ROM) |
| | U8 (7406 IC), U19 (VIC II) |
| | U9-U12 (4164 RAM), |
| | U21-U24 (4164 RAM) |
| | BT2, CR4, VR1 |
+--------------------------------------+------------------------------------+
|Out of memory error on power up. |Check U9-U12 (4164 RAM) |
| | U21-U24 (4164 RAM) |
| |**** USE DIAGNOSTIC TEST - DISK |
+--------------------------------------+------------------------------------+
|No cursor displayed. |Check U1, U15, U7 |
|Intermittent blank screen. |Check U2, U7 |
+--------------------------------------+------------------------------------+
|Powers up with graphics display and |Check U14 (74LS258 IC) |
|blinking cursor. | |
+--------------------------------------+------------------------------------+
|Powers up with all the characters |Check U26 (74LS373 IC) |
|displayed as blocks. | |
+--------------------------------------+------------------------------------+
|Intermittent display. |Check C88 (Possible Bad Connection) |
+--------------------------------------+------------------------------------+
|Powers up with the 'PRESS PLAY ON |Check U7 (6510 MPU) |
|TAPE' message and the display blanks. |R1 (Possible Bad Connection) |
+--------------------------------------+------------------------------------+
|On power up the cursor lock up. |Check U7 (6510 MPU) |
| | U20 (556 IC) |
+--------------------------------------+------------------------------------+
|When 'RETURN' is pressed after a run |Check U3 (ROM) |
|command, the cursor goes back to | |
|home position. | |
+--------------------------------------+------------------------------------+
|Poke command does not work. |Check U3 (ROM) |
+--------------------------------------+------------------------------------+
|Joystick does not operate correctly. |Check U1, U28 (6526 CIA) |
+--------------------------------------+------------------------------------+
|Wrong frequency. |Check C70 |
+--------------------------------------+------------------------------------+
|No character lettering is displayed on|Check U3 (ROM) |
|the screen. | U2 (CIA) |
+--------------------------------------+------------------------------------+
14
~
64 TROUBLESHOOTING GUIDE (Continued)
+--------------------------------------+------------------------------------+
| SYMPTOM | POSSIBLE SOLUTION |
+--------------------------------------+------------------------------------+
|Graphic characters instead of letters |Check U19 (VIC II) |
|displayed. | |
+--------------------------------------+------------------------------------+
|Power up message appears but no cursor|Check U1, U15, U7 and U4 |
+--------------------------------------+------------------------------------+
|Cursor jumps to back to home position.|Check U7 (6510 MPU) |
+--------------------------------------+------------------------------------+
|Abnormal colors appear in the letters.|Check U6 (2114 RAM) |
| | U16 (4066 IC) |
+--------------------------------------+------------------------------------+
|Diffrent characters are displayed and |Check RAM |
|cursor is locked when turned on and | |
|off. | |
+--------------------------------------+------------------------------------+
|System does not reset and the |Check U20 (556 IC) |
|'RESTORE' key does not work. | |
+--------------------------------------+------------------------------------+
|White band scrolls down the screen. |Check External Power Supply |
|(60 HZ HUM) | VR2 (5V Regulator) |
+--------------------------------------+------------------------------------+
|Cursor disappears after the system |Check U1 (6526 CIA) |
|warms up. | |
+--------------------------------------+------------------------------------+
|SYNTAX ERROR displayed after system |Check RAM, U3 (ROM) |
|warms up. | |
+--------------------------------------+------------------------------------+
|Wavy screen after the system warms up.|Check External power supply |
| | U31 (74LS629 IC) |
| | U30 (74LS193 IC) |
+--------------------------------------+------------------------------------+
|The system resets when it warms up. |Check U7 (6510 MPU) |
| | U3 (ROM) |
+--------------------------------------+------------------------------------+
|Keyboard does not operate correctly |Check U1 (6526 CIA) |
|when the system warms up. |U3 (ROM) |
+--------------------------------------+------------------------------------+
|Black band scrolls through screen |Check External Power Supply |
|when the system warms up. | C90, C88, CR4 |
| | VR2 (5V Regulator) |
+--------------------------------------+------------------------------------+
|Cassette motor keeps running. |Check U7 (6510 MPU) |
+--------------------------------------+------------------------------------+
15
~
64 TROUBLESHOOTING GUIDE (Continued)
+--------------------------------------+------------------------------------+
| SYMPTOM | POSSIBLE SOLUTION |
+--------------------------------------+------------------------------------+
|Cassette motor keeps running even |Check Cassette Port for Shorts |
|after a program is done loading. The | R4 (Possibly Open) |
|TIP 29 transistor gets extremely hot | |
|and the fuse may possibly blow. | |
+--------------------------------------+------------------------------------+
|The cursor dissappears when the |Check U7 (6510 MPU) |
|cassette is plugged in. | |
+--------------------------------------+------------------------------------+
|Cassette runs extremely slow. The |Check U7 (6510 MPU) |
|program seems to load but will not run| |
+--------------------------------------+------------------------------------+
|When loading from cassette, the |Check U20 (556 IC) |
|'SYNTAX ERROR' message is displayed. | |
+--------------------------------------+------------------------------------+
|DEVICE NOT PRESENT ERROR is displayed |Check U1 (6526 CIA) |
|when disk is used. | U7 (6510 MPU) |
| | R28, R29, R30 |
+--------------------------------------+------------------------------------+
|Disk drives continue to search when |Check U2 (6526 CIA) |
|trying to load. | |
+--------------------------------------+------------------------------------+
|When loading from disk and any key of |Check U20 (556 IC) |
|the 4th row of the keyboard is | R35 (Possible Bad Connection) |
|pressed, the cursor goes to home | |
|position. | |
+--------------------------------------+------------------------------------+
|When loading from disk, a 'FILE NOT |Check U4 (ROM) |
|FOUND' message is displayed. | U2 (6526 CIA) |
+--------------------------------------+------------------------------------+
|OUT OF MEMORY is displayed when disk |Check U20 (556 IC) |
|is used. | |
+--------------------------------------+------------------------------------+
16
~
C64 BOARD IDENFICATION
To date there are 4 version of 64 PCB assemblies in use.
VERSION IDENTIFYING FACTORS PCB ASSY # SCHEMATIC #
Original 5 pin board 326298-01 326106
(CN5-Video port has 5 pins)
A (CR) 8 pin board 250407-04 251138
(CN5-Video port has 8 pins)
B 8 pin board 250425 251469
(Reduced oscillator circuit)
B-2 8 pin board 250441-01* 251469
- These boards are interchangeable with casework, keyboard, etc.; however,
care must be taken to provide the customer with a unit that is
compatible with their monitor and cable.
- When component level repairs are neessary, be certain to acquire the
appropriate part for the board you are repairing. Most modulators are
diffrent, as are many of the components.
* The 4th version of 64 board was recently developed and only a few may be
in the field. It is termed the 64B-2. All circuits remain the same as the
64B (Schematic 251469) with a few component location changes:
1) Resistors 28, 29, 30, 36, 48 were reduced to Resistor Pack RP5.
2) Diodes CR100-105 are no longer piggybacked. Their new loactions are
CR9, 12-16.
17
~
BOARD LAYOUT #326298-01
[Figure: Board Layout #326298-01]
18
~
PARTS LIST - PCB ASSEMBLY #326298
C - Indicates Commodore Stocked Part Numbers
INTEGRATED CIRCUITS
U1,U2 6526 CIA C 906108-01
U3 2364 Basic ROM C 901226-01
U4 2364 Kernal ROM C 901227-03
U5 2364 Char ROM C 901225-01
U6 2114L-30 RAM 901453-01
U7 6510 uProcessor C 906107-01
U8 7406 901522-06
U9-U12 4164 (200 nS) 901505-01
U13 74LS257 901521-57
U14 74LS258 901521-58
U15 74LS139 901521-18
U16 4066 901502-01
U17 82S100 PLA C 906114-01
U18 6581 SID C 906112-01
U19 6567 VIC II C 906109-04
U20 LM556 901523-03
U21-U24 4161 (200 nS) 901505-01
U25 74LS257 901521-57
U26 74LS373 901521-29
U27 74LS08 901521-03
U28 4066 901502-01
U29 74LS74 901521-06
U30 74LS193 901521-26
U31 74LS629 901521-68
U32 MC4044 906128-01
TRANSISTORS
Q1 2N4401 902652-01
Q2 2N3904 902658-01
Q3 TIP29 B 902653-01
Q4-8 2N2222 902686-01
DIODES
CR1 2.7V Zener IN4371
CR2 7.5V Zener IN755
CR3 IN914
CR4 Bridge, Varo VMO8 906129-01
CR5,6 Rectifier IN4001
RESISTORS - All values are in ohms- 1/4W,
5%, unless noted otherwise.
R1 3.3K R7 10K
R2 1.5K R8 390
R3 10K R9 75
R4 1K R10 120
R5 560 R11 120
~
R6 1K R13 1K
RESISTORS (continued)
R14 100 R30 1K
R16 1K R31 180
R17 1.2K R33 47K
R19 15K R34 47K
R20 6.8K R35 470K
R21 4.7K R37 2.7K
R22 1.5K R38 1K
R23 1K R39 390
R24 3.3K R41 1M
R25 Pot 1K R43 3.3K
R26 75 R44 3.3K
R27 Pot 2K R45 3.3K
R28 1K R46 2K
R29 1K R51 1.5K
NOTE: The input video line requires a 470 ohm,
1/4 watt, resistor soldered to ground.
RESISTOR PACKS
RP1,2 33, 8 Pin (Bourne No. 430BR-102-330)
RP3 33K, 8 Pin (Bourne No. 430BR-101-332)
RP4 3.3K, 10 Pin
CAPACITORS
C1-3 Ceramic .1 uF, 50V
C4-7 Ceramic .47 uF, 50V, 20%
C8 Electrolytic 10 uF, 25V, +50%, -10%
C9 Ceramic .47 uF, 50V, 20%
C10-11 Ceramic 470 pF, 50V
C12-15 Electrolytic 10 uF, 25V, +50%, -10%
C16 Ceramic .1 uF, 50V
C17 Electorlytic 10 uF, 25V, +50%, -10%
C18 Ceramic .1 uF, 50V
C19 Electorlytic 2200 uF, 16V
C20,21 Film .22 uF, 100V, 20%
C22 Ceramic .1 uF, 50V
C23 Ceramic 360 pF, 50V
C24 Electrolytic 10 uF, 25V, +50%, -10%
C25-28 Ceramic .22 uF, 50V
C29 Ceramic .47 uF, 50V, 20%
C30,31,32 Ceramic .1 uF, 50V
C33 Ceramic .47 uF, 50V, 20%
C34 Electorlytic 10 uF, 25V, +50%, -10%
C35 Ceramic .1 uF, 50V
C36 Ceramic 20 pF, 50V
C37 Ceramic 1000 pF, 50V
19
~
PARTS LIST - PCB ASSEMBLY #326298 (Continued)
C - Indicates Commodore Stocked Part Numbers
CAPACITORS (Continued)
C38 Ceramic 51 uF, 50V
C39 Ceramic .1 uF, 50V
C40-43 Ceramic .22 uF, 25V, +50%, -10%
C44 Ceramic .47 uF, 50V, 20%
C45,46,47 Ceramic .1 uF, 50V
C48 Ceramic 1800 uF, 50V
C49 Ceramic 470 pF, 50V
C50 Ceramic .22 uF, 50V
C51 Ceramic .47 uF, 50V, 20%
C52,53 Ceramic 470 pF, 50V
C54 Ceramic .22 uF, 50V
C55 Ceramic .1 uF, 50V
C56 Ceramic .1 uF, 50V
C57 Electrolytic 10 uF, 25V, +50%, -10%
C58 Ceramic .1 uF, 50V
C59 Ceramic .22 uF, 50V
C60,61 Ceramic .47 uF, 50V, 20%
C62 Electrolytic 10 uF, 25V, +50%, -10%
C63 Ceramic .47 uF, 50V, 20%
C64,65 Electrolytic 10 uF, 25V, +50%, -10%
C66,67 Ceramic .47 uF, 50V, 20%
C68 Ceramic .1 uF, 50V
C69
C70 Mica 10 pF, 500V, 5%
C71 Ceramic .1 uF, 50V
C72 Ceramic 220 pF, 50V
C73 Ceramic 150 pF, 50V
C74 Ceramic .1 uF, 50V
C77 Ceramic .1 uF, 50V
C78 Ceramic 220 pF, 50V
C79 Ceramic 510 pF, 50V
C80 Ceramic 51 pF, 50V
C81 Ceramic 20 pF, 50V
C82 Ceramic .1 uF, 50V
C83 Mica .33 pF, 500V, 5%
C84 Ceramic .1 uF, 50V
C85 Ceramic .47 uF, 50V, 20%
C86 Mica 39 pF, 500V, 5%
C87 Ceramic .1 uF, 50V
C88 Electrolytic 470 uF, 50V
C89 Ceramic .1 uF, 50V
C90 Electrolytic 470 uF, 50V
C91 Electrolytic 100 uF, 16V
~
C92 Ceramic .22 uF, 50V
C93 Ceramic 1800 uF, 50V
CAPACITORS (Continued)
C94 Electrolytic 10 uF, 25V, +50%, -10%
C95,96 Ceramic .1 uF, 50V
C97 Ceramic .22 uF, 25V
C98,99 Ceramic .1 uF, 50V
C100 Ceramic .22 uF, 25V
C101 Ceramic .1 uF, 50V
C102 Electrolytic 10 uF, 25V, +50%, -10%
C103 Ceramic .1 uF, 50V
C105 Ceramic .1 uF, 50V
CONNECTORS
CN1 Header Assy 20 Pin 903331-20
CN4 6 Pin Din C 903361-01
CN5 5 Pin Din C 903362-01
CN6 44 Pin Card Edge C 906100-02
CN7 7 Pin Din C 906130-01
CN8,9 Plug Assy, 8 Pin Rt. Angle C 906126-01
CN10 Header Assy, 3 Pin
MISCELLANEOUS
L1,2 Coil Inductor 2.2 uH 901151-17
L3 Coil Inductor 3.0 uH 901151-21
L4 Filter Line Assy C 906127-01
L5 Coil Inductor 1.2 uH 901152-01
Y1 Crystal 14.31818 MHz C 900558-01
SW1 Rocker Switch DPDT C 904500-01
VR1 Voltage Regulator MC7812CT
VR2 Voltage Regulator MC7805CT
M1 Modulator C 326130-01
F1 Fuse, Normal Blo, 250V, 1.5A
FB1-23 Ferrite Bread 903025-01
Connector Panel
(ON, OFF, Joystick) 326299-01
Catridge Guide 326116-01
Shield Box C 326265-01
Shield Cap C 326267-01
20
~
SCHEMATIC #326106 SHEET 1 OF 2
[Figure: Schematic #326106 sheet 1 of 2]
21
~
SCHEMATIC #326106 SHEET 2 OF 2
[Figure: Schematic #326106 sheet 2 of 2]
22
~
BOARD LAYOUT #250407-04
[Figure: Board Layout #250407-04]
23
~
PARTS LIST - PCB ASSEMBLY #250407-04
C - Indicates Commodore Stocked Part Numbers
INTEGRATED CIRCUITS
U1,U2 6526 CIA C 906108-01
U3 2364 Basic ROM C 901226-01
U4 2364 Kernal ROM C 901227-03
U5 2364 Char ROM C 901225-01
U6 2114L-30 RAM 901453-01
U7 6510 uProcessor C 906107-01
U8 7406 901522-06 sub:
7416 901522-14
U9-U12 4164 (200 nS) 901505-01
U13 74LS257 901521-57
U14 74LS258 901521-58
U15 74LS139 901521-18
U16 4066 901502-01
U17 82S100 PLA C 906114-01
U18 6581 SID C 906112-01
U19 6567 VIC II C 906109-04
U20 LM556 901523-03
U21-U24 4161 (200 nS) 901505-01
U25 74LS257 901521-57
U26 74LS373 901521-29
U27 74LS08 901521-03
U28 4066 901502-01
U29 74LS74 901521-06
U30 74LS193 901521-26
U31 74LS629 901521-68
U32 MC4044 906128-01
TRANSISTORS
Q1,2 2SC1815 C 902693-01
Q3 TIP29 A 902653-01
Q7,8 2SC1815 C 902693-01
DIODES
CR1 2.7V Zener IN4371 906103-02
CR2 7.5V Zener IN755 900941-01
CR4 Bridge S2VB10 C 251026-01
DBA20B C 251026-02
DBA20C C 251026-03
CR5,6 Rectifier IN4001 900750-01
RESISTORS - All values are in ohms- 1/4W,
5%, unless noted otherwise.
R1 3.3K R6 1K
R2 1.5K R7 10K
R3 10K R16 1K
R4 1K R17 2.7K
~
R5 560 R19 15K
RESISTORS (continued)
R26 75 R39 390
R27 Pot 2K R41 1M
R28 1K R42 82
R29 1K R43 3.3K
R30 1K R44 3.3K
R31 180 R45 3.3K
R33 47K R50 1M
R34 47K R51 1.5K
R35 470K R52 300
R36 1K R53 390
R37 2.7K R100 1K
R38 1K R101 22K
RESISTOR PACKS
RP1,2 33, 8 Pin (Bourne No. 430BR-102-330)
RP3 33K, 8 Pin (Bourne No. 430BR-101-332)
RP4 3.3K, 10 Pin
CAPACITORS
C1-7 Ceramic .1 uF, 25V
C8 Electrolytic 10 uF, 25V, +50%, -10%
C9 Ceramic .1 uF, 25V
C10,11 Ceramic 470 pF, 50V
C12 Ceramic .1 uF, 25V
C13,14,15 Electrolytic 10 uF, 25V, +50%, -10%
C16 Ceramic .1 uF, 25V
C17 Electorlytic 10 uF, 25V, +50%, -10%
C18 Ceramic .1 uF, 25V
C19 Electorlytic 2200 uF, 16V
C20,21 Film .22 uF, 100V, 20%
C22 Ceramic .1 uF, 25V
C23 Ceramic 360 pF, 50V
C24 Electrolytic 10 uF, 25V, +50%, -10%
C25-33 Ceramic .1 uF, 25V
C34 Electorlytic 10 uF, 25V, +50%, -10%
C35 Ceramic .1 uF, 50V
C36 Ceramic 20 pF, 50V, 5% SL
C37 Ceramic 1000 pF, 50V, 10% B
C38 Ceramic 51 uF, 50V, 5% SL
C39-47 Ceramic .1 uF, 25V
C48 Ceramic 1800 pF, 50V, 10% B
C49-54 Ceramic .1 uF, 25V
C55 Ceramic .1 uF, 50V
C56 Ceramic .1 uF, 25V
C57 Electrolytic 10 uF, 25V, +50%, -10%
C58 Ceramic .1 uF, 50V
24
~
PARTS LIST - PCB ASSEMBLY #250407-04 (Continued)
C - Indicates Commodore Stocked Part Numbers
CAPACITORS (Continued)
C59,60 Ceramic .1 uF, 25V
C62,65 Electrolytic 10 uF, 25V, +50%, -10%
C66,67,68 Ceramic .1 uF, 25V
C70 Film 16 pF, 5%
C74,82 Ceramic .1 uF, 25V
C83 Ceramic 82 pF, 5%
C84 Ceramic .1 uF, 25V
C85 Ceramic .47 uF, 50V, 10%
C88 Electrolytic 1000 uF, 25V
C89 Ceramic .1 uF, 25V
C90 Electrolytic 470 uF, 50V
C91 Electrolytic 100 uF, 16V, +50%, -10%
C92 Ceramic .1 uF, 25V
C93 Ceramic 1800 pF, 50V, 10% B
C94 Electrolytic 10 uF, 25V, +50%, -10%
C95,96 Ceramic .1 uF, 25V
C97 Ceramic .22 uF, 25V
C98,99 Ceramic .1 uF, 25V, +80%, -20%
C100 Ceramic .22 uF, 25V
C101 Ceramic .1 uF, 50V, +80%, -20%
C102 Electrolytic 10 uF, 25V, +50%, -10%
C103 Ceramic .1 uF, 25V
C104
C105 Ceramic .1 uF, 25V
C108 Electrolytic 10 uF, 25V, +50%, -10%
C200 Ceramic .1 uF, 25V
CONNECTORS
CN1 Header Assy 20 Pin 903331-20
CN4 6 Pin Din C 903361-01
CN5 8 Pin Din C 325573-01
CN6 44 Pin Card Edge C 906100-02
CN7 7 Pin Din C 251116-01
CN8,9 Plug Assy, 9 Pin MINID C 906126-01
CN10 Header Assy, 3 Pin 903332-03
MISCELLANEOUS
L2 Coil Inductor 2.2 uH 901151-17
L4 Coil Inductor 1.2 uH 325570-01
L5 Choke Coil C 325559-02
Y1 Crystal 14.31818 MHz C 900558-01
SW1 Rocker Switch DPDT C 904500-01
VR1 Voltage Regulator MC7812CT 901527-01
~
VR2 Voltage Regulator MC7805CT 901527-02
M1 Modulator C 251080-01
F1 Fuse, Normal Blo, 250V, 1.5A
FB1-23 Ferrite Bread 903025-01
Connector Panel
(ON, OFF, Joystick) 251095-01
Catridge Guide 326116-01
Shield Box C 251023-01
Shield Cap C 251024-01
25
~
MODULATOR SCHEMATIC #251025
[Figure: Modulator schematic #251025]
SCHEMATIC #251138 SHEET 1 OF 2
[Figure: Schematic #251138 sheet 1 of 2]
26
~
SCHEMATIC #251138 SHEET 2 OF 2
[Figure: Schematic #251138 sheet 2 of 2]
27
~
BOARD LAYOUT #250425-01
[Figure: Board Layout #250425-01]
28
~
PARTS LIST - PCB ASSEMBLY #250425-01
C - Indicates Commodore Stocked Part Numbers
INTEGRATED CIRCUITS
U1,U2 6526 CIA C 906108-01
U3 2364 Basic ROM C 901226-01
U4 2364 Kernal ROM C 901227-03
U5 2364 Char ROM C 901225-01
U6 2114L-30 RAM 901453-01
U7 6510 uProcessor C 906107-01
U8 7406 901522-06 sub:
7416 901522-14
U9-U12 4164 (200 nS) 901505-01
U13 74LS257 901521-57
U14 74LS258 901521-58
U15 74LS139 901521-18
U16 4066 901502-01
U17 82S100 PLA C 906114-01
U18 6581 SID C 906112-01
U19 6567 VIC II C 906109-04
U20 LM556 901523-03
U21-U24 4161 (200 nS) 901505-01
U25 74LS257 901521-57
U26 74LS373 901521-29
U27 74LS08 901521-03
U28 4066 901502-01
U31 7701/8701 C 251527-01
TRANSISTORS
Q1 TIP29 A 902653-01
Q2-4 2SC1815 C 902693-01
DIODES
CR1 2.7V Zener IN4371 906103-02
CR2 6.8V Zener IN755
CR4 Bridge S2VB10 C 251026-01 sub:
DBA20B C 251026-02 sub:
DBA20C C 251026-03
CR5,6 Rectifier IN4001 900750-01
CR9, IN4148 sub:
CR12-16 IN914
CR100-105
RESISTORS - All values are in ohms- 1/4W,
5%, unless noted otherwise.
R1 3.3K R26 3.3K
R2 1.5K R31 180
R3 10K R33 47K
R4 1K R34 47K
R5 560 R35 470K
~
R6 1K R37 2.7K
R7 10K R38 1K
RESISTORS (continued)
R39 390 R50 1M
R41 1M R51 1.5K
R42 82 R60 100
R43 3.3K R100 1K
R44 3.3K R101 22K
R45 3.3K
RESISTOR PACKS
RP1,2 33, 8 Pin (Bourne No. 430BR-102-330)
RP3 33K, 8 Pin (Bourne No. 430BR-101-332)
RP4 3.3K, 10 Pin
RP5 1K, 6 Pin
CAPACITORS
C1-7 Ceramic .1 uF, 25V
C9 Ceramic .1 uF, 25V
C10,11 Ceramic 470 pF, 50V, 10%
C12 Ceramic .1 uF, 25V
C13 Electrolytic 10 uF, 25V, +50%, -10%
C15 Tantalum 4.7 uF, 16V, 20%
C19 Electorlytic 2200 uF, 16V
C20 Film .22 uF, 100V, 20%
C22 Ceramic .1 uF, 25V
C23 Ceramic 360 pF, 50V, 10% sub: 390 pF
C24 Electrolytic 22 uF, 25V, +50%, -10%
C31,33,34 Ceramic .1 uF, 25V
C37 Ceramic 1000 pF, 50V, 10% B
C38 Ceramic 51 pF, 50V, 5% SL
C39-46 Ceramic .1 uF, 25V
C48 Ceramic 1800 pF, 50V, 10% B
C50,51,53 Ceramic .1 uF, 25V
C59 Ceramic .1 uF, 25V
C88 Electrolytic 1000 uF, 25V
C90 Electrolytic 470 uF, 50V
C91 Electrolytic 100 uF, 16V, +50%, -10%
C93 Ceramic 1800 pF, 50V, 10% B
C101 Ceramic .1 uF, 50V, +80%, -20%
C102 Electrolytic 10 uF, 25V, +50%, -10%
C150-152 Ceramic 470 pF, 50V, 10%
C153 Ceramic 68 pF, 50V, 5%
C154 Ceramic 470 pF, 50V, 10%
C200 Ceramic .1 uF, 25V
C204 Ceramic 150 pF, 50V, 10%
C205 Ceramic 220 pF, 50V, 5%
CT1 Trimmer 40 pF
29
~
PARTS LIST - PCB ASSEMBLY #250407-04 (Continued)
C - Indicates Commodore Stocked Part Numbers
CONNECTORS
CN1 Header Assy 20 Pin 903331-20
CN4 6 Pin Din C 903361-01
CN5 8 Pin Din C 325573-01
CN6 44 Pin Card Edge C 906100-02
CN7 7 Pin Din C 251116-01
CN8,9 Plug Assy, 9 Pin MINID C 251057-01
CN10 Header Assy, 3 Pin 903332-03
MISCELLANEOUS
L2 Coil Inductor 2.2 uH 901151-17
L4 Line Filter Assy C 251701-01
L5 Coil Inductor 1.2 uH 901152-01
Y1 Crystal 14.31818 MHz C 251707-01
SW1 Rocker Switch DPDT C 904500-01
VR1 Voltage Regulator MC7812CT 901527-01
VR2 Voltage Regulator MC7805CT 901527-02
M1 Modulator C 251696-01
Connector Panel
(ON, OFF, Joystick) 251095-01
Catridge Guide 326116-01
F1 Fuse, Normal Blo, 250V, 1.5A
30
~
MODULATOR SCHEMATIC #251696
[Figure: Modulator schematic #251696]
SCHEMATIC #251469 SHEET 1 OF 2
[Figure: Schematic #251469 sheet 1 of 2]
31
~
SCHEMATIC #251469 SHEET 2 OF 2
[Figure: Schematic #251469 sheet 2 of 2]
32
~
U1, U2 - 906108-01
6526 COMPLEX INTERFACE
ADAPTER (CIA)
PIN 1 VSS Ground connection
ASSIGNMENT 2-9 PA0-PA7 Parallel port a signals.
+----------+ Bidirectional parallel port.
| | 10-17 PB0-PB7 Parallel port b signals.
GND-+ 1 40+-CNT Bidirectional parallel port.
PA0-+ 2 39+-SP 18 PC Handshake output. A low pulse is
PA1-+ 3 38+-RS0 generated after a read or write
PA2-+ 4 37+-RS1 on port b.
PA3-+ 5 36+-RS2 19 TOD Time od day clock input.
PA4-+ 6 35+-RS3 Programmable 50hz or 60hz.
PA5-+ 7 34+-_RES 20 VCC 5VDC input.
PA6-+ 8 33+-DB0 21 IRQ Interrupt output to microprocessor
PA7-+ 9 32+-DB1 input IRQ.
PA0-+10 31+-DB2 22 R/W READ/WRITE input from
PB1-+11 20+-DB3 microprocessor's R/W output.
PB2-+12 29+-DB4 23 CS Chip select input. A low pulse
PB3-+13 28+-DB5 will activate CIA.
PB4-+14 27+-DB6 24 FLAG Negative edge sensitive interrupt
PB5-+15 26+-DB7 input. Can be used as a handshake
PB6-+16 25+-O2 line for either parallel port.
PB7-+17 24+-_FLAG 25 O2 O2 clock input. Connected to
PPC-+18 23+-_CS processor common O2 clock.
TOD-+19 22+-R/_W 26-33 DB0-DB7 Bidirectional data bus. Connects
VCC-+20 21+-_IRQ to processor data bus.
| | 34 RES Low active reset input.
+----------+ Initializes CIA.
35-38 RS0-RS3 Register select inputs. Used to
select all internal registers
for communications with the
parallel ports, time of day
clock and serial port (SP).
39 SP Serial Port bidirectional
connection. An internal shift
register conveerts
microprocessor parallel data
into serial data, and vice
versa.
40 CNT Count input. Internal timers
can count pulses applied to
this input. cAn be used for
frequency dependant operations.
~
U18 - 906112-01
6581 SOUND INTERFACE
DEVICE (SID)
PIN 1,2, CAP1A,1B
ASSIGNMENT 3,4 2A,2B Capacitor filter connections
+----------+ 5 RES Reset input. A low pulse
| | initializes the SID.
CAP-+1A 28+-12V 6 O2 Processor phase 2 clock input.
CAP-+1B 27+-A.OUT 7 R/W Processor read/write input.
CAP-+2A 26+-EXT IN 8 CS Chip select input.
CAP-+2B 25+-5V 9-13 A0-A4 Address lines from processor.
_RES-+ 5 24+-POT X 14 GND Dc ground connection.
O2-+ 6 23+-POT Y 15-22 D0-D7 Data Bus connections.
R/_W-+ 7 22+-D7 23 POT Y Input to a A/D converter used to
_CS-+ 8 21+-D6 detect the value of a variable
A0-+ 9 20+-D5 resistor. Commonly connected to
A1-+10 19+-D4 game paddles.
A2-+11 18+-D3 24 POT X Same as POT Y.
A3-+12 17+-D2 25 VCC 5VDC.
A4-+13 16+-D1 26 EXT IN External audio input.
GND-+14 15+-D0 27 A.OUT Audio output. Should be AC coupled
| | to audio amp.
+----------+ 28 Vdd 12VDC.
33
*********
End of the Project 64 etext of the Commodore 64 Service Manual.
*********
|