Texas Instruments 990 - Page 55

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Main Page

Table of Contents5
Paragraph Title Page6
Section I. Theory of Operation11
General11
System Description11
CRT Monitor12
Power/Logic PWB13
VDT Controller17
Interface Descriptions19
VDT Controller/Computer Interface20
Single-Bit Operations20
Multiple-Bit Operations20
Hardware Interface Signals22
Keyboard Data (KBDT, 1-8)28
Keyboard Data Strobe (KBSIN-)29
Power/Logic PWB-To-VDT Controller Interface29
Keyboard Data (TET,1,2,T)29
Terminal Ready (TRD, 1, 2, T)29
VDT Controller-To-Power/Logic PWB Interface29
Beep Enable (BET, 1, 2, T)32
Modem Audio (MODIN)32
Principles of Operation33
Mode Keys and Mode Select Logic33
Power/Logic PWB34
Buffer Register45
LED Display45
Difference Amplifier53
CRT Monitor54
CRT Interface Logic56
Built-In Test Logic56
Keyboard Logic57
Model 911 VDT Controller Block Diagram59
Video Line Driver61
CRU Interface Logic62
Model 911 VDT Keyboard Logic63
CRU Interface Logic65
Refresh Memory and Control Logic69
Refresh Memory Block Diagram70
Refresh Memory Data Path73
Memory Read and Write Control Logic75
Memory Addressing Logic77
Flowchart for Memory Write Operation79
Flowchart for Memory Read Operation80
Display Screen Refresh Cycle Flowchart81
Video Output Logic83
Model 911 VDT Character Matrix Formats85
Model 911 VDT Displayed United States Character Set, Including Graphics Symbols87
Model 911 VDT Alarm Logic89
Model 911 VDT Time Base Generator Character Synchronization Logic93
Model 911 VDT Dot Counter Outputs95
Model 911 VDT Sync Timing Diagram101
Section II. Maintenance103
General103
Maintenance Philosophy103
Special Test Equipment103
Model 990 Computer Hot Mock-Up System for 60-Hertz Model 911 VDT Testing104
Hot Mock-Up System106
Loading the Diagnostic106
Using the Diagnostic106
CD Verb Entry109
General Maintenance Procedures110
PWB Preliminary Checkout110
General Fault Isolation Procedures110
Keyboard Maintenance Procedures110
Keyboard Preliminary Checkout110
Keyboard Fault Isolation Procedures111
Keyboard Operational Checkout114
Power/Logic PWB Maintenance Procedures114
Power/Logic PWB Preliminary Checkout115
Power/Logic PWB Fault Isolation Procedures115
VDT Controller Maintenance Procedures115
VDT Controller Fault Isolation Procedures118
CRT Monitor Maintenance Procedures118
CRT Monitor Preliminary Checkout118
CRT Monitor Fault Isolation Procedures118
VDT Controller Assembly Configuration119
CRU Interface Waveforms During Exercise by the CD-C Verb125
Timer Signal Relationships128
Alarm Signal Timing Diagram131
Model 911 VDT Controller Keyboard Logic Timing Diagram133
United Kingdom Model 911 VDT Keyboard Arrangement, Hexadecimal Codes, Mode Character Positions, ASCII, Special Character Set, and Matrix Chart147
United Kingdom Model 911 VDT Keyboard Matrix Chart153
French Model 911 VDT Keyboard Arrangement, Hexadecimal Codes, Mode Character Positions, ASCII, Special Character Set, and Matrix Chart154

Texas Instruments 990 - Page 55

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