Radio Shack TRS-80 User manual

TRS-BO®
MODELm
MICROCOMPUTER
•
ervlce
Catalog Numbers 26-1061/1062/1063
/
CUSTOM MANUFACTURED IN U.S.A. BY RADIO SHACKl!A DIVISION OF TANDY CORPORATION

SECTION
NUMBER
II
'"
IV
V
VI
TABLE OF CONTENTS
INTRODUCTION ..
System Overview
DISASSEMBLY/REASSEMBLY ..............••...
Disa5Sembly .................•••••...••.•..
Reassembly ...........................••..
CPU CIRCUIT BOARD ..•...•• ~ •..••••••....•..
Technical Description .......•.....•.••••..•..
Video Sync Circuits ....•.•..............••.
Processor ...........••••••••••••....•..
RAM ...............•...........•.••..
Addrcs.s Decoding ........••...............
Memory Map ..........•••••••••.........
10 PORT Description ......•••..•.•••••••..
Video .
Keyboard
....................•.........
Cassette Interface ..................•......
line Printer and Real Time Clock .......••••••.
10 Bus •.............................•.
Adjustments and Jumper Positions .
Model III 10 Bus Detailed Description ....•......
Model III PORT Bits ................•••.•..
CPU Module Parts List .................••••••.
FLOPPY DISK INTERFACE .
Technical Description .
Control and Data Buffering .
Non ·Maskable Interrupt Logic .
Drive Select Latch and Motor
On Logic .
Wait State Generation and WAITIMOUT Logic
Clock Generation Logic .
Disk Bus Selector Logic .
ReadlWrite Data Pulse Shaping Logic .
Disk Bus
Output Drives .
Write Preoompensation and Clock Recovery Logic
Floppy Disk Controller Chip .
Adjustments and Jumper Options .
Floppy Disk Interface
PC Board Parts List , .
RS-232C CIRCUIT
BOARD. . .
RS-232C Technical Description .........•••••.
Pin ·Out Description . .••••....•..•.
Port and Bit Assignments .
RS·232C
PC Board Parts List .....•••••.......
POWER SUPPLY . . . . . . . . . . . . ..••.•.
Functional Specifications .......•••••..••.••••.
Troubleshooting. . . ......•..••....••.•.
Set-Up Procedures .....................••••.
Visuiliinspec.:tion .........................•.
Surt-Up . . . ...................••..
No Output ..............•••••.•••..
Perfonnilnce Test ................••..•..
Power Supply Component ViIIlues ............•••.
PAGE
NUMBER
1
3
5
7
9
11
13
13
13
13
14
"
15
16
17
17
,.
,.
,.
19
21
25
.,
.3
.3
43
43
44
44
44
44
44
44
45
45
49
53
55
56
57
62
65
67
67
67
67
58
58
69
70

SECTION
NUMBER
VII
VIII
IX
TABLE OF CONTENTS (Cont'd)
VIDEO MONITOR . ..........•... _ _ .
Functional Specifications . .................•...
Se...,ice Adjustments .
ILLUSTRATED PARTS CATALOG
Illustrated Parts Catalog Parts list
MINI·DISK DRIVE .
General Description .............•...........
Introduction ...............••...........
Important Notice ........•••..............
Physical Description .......•..•............
Functional Desaiption ........•..•.........
Interface Connections ........•.•••.........
Physical Checkout ...........••.•.........
Mounting the Disk Drive .......••.•.....
Resistor Termination . .........••.•.........
Flat Ribbon Cable Assembly .
Theory of Openrtion .
Introduction .
Organization of the Disk Drive .
Functional Block Diagram Description .
Indell Pulse .
Write Protect .
Track 00 Switch : .
Spindle Drive . ................•.•......
Positioner Control .
Data Electronics . ..........••.•...........
Data Recording .
Data Reproduction .
Operation .
Interface Electronics Specifications ......•......
Input Control Lines .
SELECT Lines IDS'- - DS4-) .
Drive Motor Enable (MOTORQN) .
Direction and Step (DIA-) (STEP-' .
Compensated Write Data (CWO) ..•.....
Write Enable (WG-) .
Side Select (SDSE
L) .
Output Status .
Index Pulse liP') .
TRACK OOITAKO-j . .....•......•.........
Write Protect (WPRT', .
Read Data (RD-) .................•.......
Maintenance .
Physical Oesaiption of the PC Boards .
Circuit Board Test Points .
Option Select .
Input Line Terminations ....••.............
Pr ... entive Maintenance .. _ .......•••..........
Cleaning the Head ............••...........
Alignment anet Adjustment .
Drive Motor Maintenance .
Carriage Movement Check .
Head Radiel Alignment/CE Alignment .
Track 013 Alignment .
Index Sector Adjustment .
Head Amplitude/Compliance Oleck .
PAGE
NUMBER
73
7S
77
79
8.
91
93
93
93
.3
93
93
94
9.
9.
9.
97
97
97
97
97
97
97
97
97
98
..
..
101
101
101
101
101
101
101
101
103
103
103
103
103
103
lOS
lOS
lOS
lOS
lOS
108
108
108
108
108
109
110
110
111

SECTION
NUMBER
TABLE OF CONTENTS (Cont'dl
PAGE
NUMBER
FIGURE
NUMBER
FiNI Check .
Disk Controller Board Parts List .
SalVo Board Parts List (Non-Linear) .......••.
Servo Board Parts list (linear) .. . ....•....••..
Illustrated Parts Catalog Parts Lin .
LIST OF ILLUSTRATIONS
TiTlE
SECTION 1- INTROOUCTION
TAS.aO Model III Block Diagram .
SECTION
III -CPU CIRCUIT BOARD
111
112
118
117
119
PAGE
NUMBER
4
1
2
3
4
4
5A
58
5C
5D
5E
5F
5G
5H
5J
5K
1
2
2
3
CPU Timing Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . • . . . . . . 13
Video Timing Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . .
•• • . . . . . . 16
10 Bus Timing Diagram .. . . . . . . . . . . . . . . . . . . . . . • • . . . • • • • • . . . 20
CPU Printed Circuit Board -Component Side. . . . . • • • . • • . • • • • • • . .. 23
CPU Printed Circuit Board _Circuit Side . . . . . • . . . . . 24
Model III CPU Schlml"tic Diagram -
Video and Horizontal Sync
Circuit!> . . . . . . . . . . . . . . . . . . . . . . • • . .. 31
Model
III CPU SChematic Diagram -Processor Section . . . . . • • . . • • • . .. 32
Model
III CPU Schematic Diagram - RAM Section. . . . . . . . . . . . • • • . .. 33
Model 111 CPU Schematic Di"gram-
Address De"coding Section ............................•.... 34
Model
III CPU Schematic Diagram -Video section... ........••.. .. 35
Model
III CPU Schematic Diagram -Keyboard Section. . . . . . . •••. •. . . 36
Model
III CPU Schematic Diagram-
Cassette Interface Section. . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . .. 37
Model III CPU Schematic Diagram -
Line Printer and
Real Time Clock Section .. . . . . . . . . . . . • • • • • . • . . . 38
Model 11/ CPU Schematic Diagram -I/O Bus Section .......•.•...... 39
Model III CPU Schematic Diagram -
RS·232C Interface and FDC Interface
Connections. . . . . • • • • • • • • • . .. 40
SECTION IV - flOPPY DISK INTERFACE
FOC Board to
CPU Board Signal Description. . . . . . . . . . • • • • • . . . . . . . 46
Floppy Did< Interface PC Board -Component Side ..........••... 47
Floppy
Dilik Interface PC Board -Circuit Side ...........•••..... 48
Model III Floppy Disk Interface SChematic... ... ....•..•.••.... 51

FIGURE
NUMBER
1
,
,
3
LIST OF ILLUSTRATIONS (Cant'd)
TITLE
SECTION V-R5-232C CIRCUIT BOARD
R5-232C Board
to CPU Board Signal Description
AS·232C PC Board - Component Side
RS·232C
PC Board -Circuit Side .
Model
til RS·232C Schematic Diagram .
SECTION VI -POWER SUPPLY
PAGE
NUMBER
5.
60
61
63
1
,
3
•
Ten Set-Up . . . . . . . . . . . . . . . . . . . . . . . . . • • • . . . . . . . . . . . . . . .. 67
02 Coll&ctor Waveform . . . . . . . . . . . . . . • . . . • • • . • . • • • • • . 68
02 Bue Waveform . . . . . . . . . . . . . . . . • • . • • • • . . • . • • . . . 68
Power Supply 5ct1ematic Diagram ..••• , . . . . . . . 71
SECTION VtI- VIDEO MONITOR
1
,
3
Video Monitor Printed Circuit Board .......................•...
Deflection Yoke Assembly .
Video Monitor Assembly Sd1ematic Diagram
...........••..••.•..
SECTION VIII -ILLUSTRATED PARTS CATALOG
76
77
78
1
,
3
•
5
1
1A
2
3
•
5
6
7
8
8
10
11
12
13
"
15
16
17
18
18
,.
20
20
Outer Case Assembly. ..................... ......... .. 81
Case Top Assembly. ...........................•••••.... .. 82
Base Plate Assembly .......••...••.•••.••••...•........... 83
Metal Chassis Assembly .. . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . 84
Disk Drive Assembly . . . . . . . . . . . . . . . . . • . . • . . . . . . . . • . . .. 85
SECTION IX -FLOPPY DISK DRIVE
PC Board Component Locations (Logic Board) . . . .
.. ........ .. 94
PC Boord Components Locations (servo Boards)
..............•.... 95
Resistor Termination. . . . . . . . . . . . . . . . . . . . . . . . • • . • • • . . • . . . .. 96
Cable Assembly - Connector Pin Removal Chart ....••.•••••....... 96
Funetional Blode Diagram 98
FM Recording .............................•..•••.•.•. 98
Write Timing Diagram. ... .. . . . .. ............... .• .•• .100
Read Timing Diagram .................... .......
100
Interface Configuration.. . . . . .. . . . . .. . . . . . . . . •. . . . . .. . . . . 101
Logic Board Test Points and Connector Locations ....••.••••••••. 106
Servo Board Comector Locations.. . . . . .. ... .. . . .. . .. .•. .. . . 107
"Cat's Eyes" Panern .. .................................. .. 109
Radial Ad;ustmeot ..................•..•••••........•.... 109
Track
tJ0 Stop Adjustment . • • • • . . . • • • • • • • • . • • • . . • . 110
Index Sector Timing .. . . . . . . . . . . . . . . . . . . • . • . • • . . . . • . . . . . 110
Index
Adjustment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Upper Arm and Carriage
.................••••............. 111
Illustrated Parts Catalog -Exploded View .....•••••••.••.•••.... 118
Mini·Disk Drive Schematic (Sheet
11 ........••.•••••.•••••.•.. 120
Mini-Disk Drille Schematic (Sheet 2) ..........••••............. 121
Servo Board Schematic .....................•.............. 122
Mini·Disk Drive Schematic (new board) ............ ••••. . . 123
Mini·Disk Drive Schematic (new
boardl ....• ,.................. 124

TABLE
NUMBER
LIST OF TABLES
TITLE
SECTION V - R5-232C CIRCUIT BOARD
PAGE
NUMBER
1
2
1
2
BRG Programming Table .
SECTION VI- POWER SUPPLY
Load Board Values. ...... . ............••••..•..•....
Voltage and Ripple Specifications ....
SECTION IX - MINI·DISK DAIVE
Interface Connector Pin Assignments .............•...
Power Connector Pin Assignmcots ...............•.••.
55
58
59
'02
'02

SECTION I
INTRODUCTION
,

SYSTEM OVERVIEW
The Aadio 5tIack TASSO Model III Miaocomputer is an enhanced venion of Aadio 5tIack's popular TRsaO Microcom-
puter (Model n. The TAs-80 Model III is sohware eompatible with the Modell §() thillt ownenof either system can take
adll8ntilge
of the large number of programs available.
Features of the TAS-80 Model III which are common to the TR5-80 Modell include:
•Availability of Level lor Level II BASIC in ROM
• Full size typewriter style keyboard
• A 12-inch video display
•Built·in cassette interface
•Character display
of 16 lines of 64 characters
•Graphics under control
of BASIC (128 H x 48 VI
• UL reoognized construction
In addition. tne Model III has the following standard features:
•12-«.ey numeric keypad for rapid entry of numbers
• Augged cabinet housing keyboard. electronics, video display. and power supply
•Direct drive video monitor for improved resolution
•Internal power supply
•Parallel printer port for
USll with Aadio 5tIack printers
several
other features are available when Level II BASIC is used; features such as: real time clock, upper and lower case
characters,
RAM internally expandable to 48K bytes, I/O l)Or\ for peripheral expansion. and cassette interface available
with
500 aoo 1500 baud rates.
Optional peripherals for the TAS-aO Model
III include disk drives (two built·in, two external) with double density for
increased storage capacity. and ahuilt·in R5-232 serial interface for communications and peripheral interface.
The Block Diagram shows the various internal components and connections of the Model III Microcomputer.
3