Radio Shack TRS-80 Service Manual page 4

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