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Texas Instruments 990 User Manual
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Table
1-11.
Model
911
VDT
Row
Decoder
ROM
Table
ROM
INPUTS
ROM
OUTPUTS
REMARKS
~
~
~
x
x
x
x
0
0
0
ROW12
,3C0-3FF
50
HZ
x
0
0
0
960
CHAR
0
0
0
ROW20,640-67F,CHAR
99
PN
948554-8
x
x
0
0
0
0
0
0
0
ROW
16,500-53F
x
x
0
0
0
0
0
ROW24,
780-7BF
'""""
50
HZ
I
0
0
0
0
0
1920
CHAR
0
0
0
ROW32,AOO-A3F,CHAR
99
00
PN
\C
948
554-6
x
x
0
0
0
0
0
0
ROW27
,840-87F
x
x
x
x
60
HZ
0
0
0
ROWl
2
,3C0-3FF
960
CHAR
x
x
0
0
PN
0
0
0
ROW17,
540-57F,
ChAR
99
948554-4
x
x
x
0
0
0
0
0
0
ROWl
4
,440-47F
x
x
x
0
60
HZ
0
0
0
ROW24,
780-7BF
1920
CHAR
0
0
0
0
0
PN
0
0
0
ROW27
,880-SBF,
CHAR
99
948554-2
x
x
x
0
0
0
ROW25,
7C0-7FF
0
<§:
NOTE:
ROW
DECODES
ARE
FOR
THE
CHAR.ACTER
COUNT
AT
TIME
HDSL
WHICH
IS
NORMALLY
CHARACTER
TIME
82
-
SINCE
END
IS
AN
EVENT
THAT
OCCURS
AT
THE
END
OF
A
LINE
(CHARACTER
TIME
99),
THE
DECODE
ADDRESS
~
IS
THE
ONE
WHICH
WILL
BE
VALID
AT
K99L
TIME.
(/)
~
<D
3
Cl)
0
(A)
1
36307
~-
c;;·
a·
::J
98
100
Table of Contents
Table of Contents
5
Paragraph Title Page
6
Section I. Theory of Operation
11
General
11
System Description
11
CRT Monitor
12
Power/Logic PWB
13
VDT Controller
17
Interface Descriptions
19
VDT Controller/Computer Interface
20
Single-Bit Operations
20
Multiple-Bit Operations
20
Hardware Interface Signals
22
Keyboard Data (KBDT, 1-8)
28
Keyboard Data Strobe (KBSIN-)
29
Power/Logic PWB-To-VDT Controller Interface
29
Keyboard Data (TET,1,2,T)
29
Terminal Ready (TRD, 1, 2, T)
29
VDT Controller-To-Power/Logic PWB Interface
29
Beep Enable (BET, 1, 2, T)
32
Modem Audio (MODIN)
32
Principles of Operation
33
Mode Keys and Mode Select Logic
33
Power/Logic PWB
34
Buffer Register
45
LED Display
45
Difference Amplifier
53
CRT Monitor
54
CRT Interface Logic
56
Built-In Test Logic
56
Keyboard Logic
57
Model 911 VDT Controller Block Diagram
59
Video Line Driver
61
CRU Interface Logic
62
Model 911 VDT Keyboard Logic
63
CRU Interface Logic
65
Refresh Memory and Control Logic
69
Refresh Memory Block Diagram
70
Refresh Memory Data Path
73
Memory Read and Write Control Logic
75
Memory Addressing Logic
77
Flowchart for Memory Write Operation
79
Flowchart for Memory Read Operation
80
Display Screen Refresh Cycle Flowchart
81
Video Output Logic
83
Model 911 VDT Character Matrix Formats
85
Model 911 VDT Displayed United States Character Set, Including Graphics Symbols
87
Model 911 VDT Alarm Logic
89
Model 911 VDT Time Base Generator Character Synchronization Logic
93
Model 911 VDT Dot Counter Outputs
95
Model 911 VDT Sync Timing Diagram
101
Section II. Maintenance
103
General
103
Maintenance Philosophy
103
Special Test Equipment
103
Model 990 Computer Hot Mock-Up System for 60-Hertz Model 911 VDT Testing
104
Hot Mock-Up System
106
Loading the Diagnostic
106
Using the Diagnostic
106
CD Verb Entry
109
General Maintenance Procedures
110
PWB Preliminary Checkout
110
General Fault Isolation Procedures
110
Keyboard Maintenance Procedures
110
Keyboard Preliminary Checkout
110
Keyboard Fault Isolation Procedures
111
Keyboard Operational Checkout
114
Power/Logic PWB Maintenance Procedures
114
Power/Logic PWB Preliminary Checkout
115
Power/Logic PWB Fault Isolation Procedures
115
VDT Controller Maintenance Procedures
115
VDT Controller Fault Isolation Procedures
118
CRT Monitor Maintenance Procedures
118
CRT Monitor Preliminary Checkout
118
CRT Monitor Fault Isolation Procedures
118
VDT Controller Assembly Configuration
119
CRU Interface Waveforms During Exercise by the CD-C Verb
125
Timer Signal Relationships
128
Alarm Signal Timing Diagram
131
Model 911 VDT Controller Keyboard Logic Timing Diagram
133
United Kingdom Model 911 VDT Keyboard Arrangement, Hexadecimal Codes, Mode Character Positions, ASCII, Special Character Set, and Matrix Chart
147
United Kingdom Model 911 VDT Keyboard Matrix Chart
153
French Model 911 VDT Keyboard Arrangement, Hexadecimal Codes, Mode Character Positions, ASCII, Special Character Set, and Matrix Chart
154
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Texas Instruments 990 Specifications
General
Brand
Texas Instruments
Model
990
Category
Desktop
Language
English
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