Radio Shack TRS-80 Service Manual page 2

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
"
1 5
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