VT220 Technical Manual

Company:	Digital Equipment Corporation
Part:	EK-VT220-TM-001
Date:	1984-11

Chapter 1 System Introduction
- 1.1 General
- 1.2 Physical Description
  - 1.2.1 Monitor Assembly (VT220)
  - 1.2.2 Keyboard (LK201)
  - 1.2.3 Modem Module Option (VT22X-AA)
- 1.3 Display Characteristics and Capabilities
- 1.4 Communication Environment
- 1.5 Major Operating States
- 1.6 Operating Modes
  - 1.6.1 VT100 Mode
  - 1.6.2 VT200 Mode, 7-Bit Controls
  - 1.6.3 VT200 Mode, 8-Bit Controls
  - 1.6.4 VT52 Mode
Chapter 2 Controls, Indicators, and Connectors
- 2.1 General
- 2.2 Monitor Assembly (VT220)
- 2.3 Keyboard (LK201)
  - 2.3.1 Main Keypad
  - 2.3.2 Editing Keypad
  - 2.3.3 Auxiliary Keypad
  - 2.3.4 Top-Row Function Keys
  - 2.3.5 Visual Indicators
  - 2.3.6 Audible Indicators
    - 2.3.6.1 Audible Keyclick
    - 2.3.6.2 Bell
  - 2.3.7 Connector Cable
- 2.4 Modem Option (VT22X-AA)
Chapter 3 System Overview
- 3.1 General
- 3.2 Operating States
  - 3.2.1 Set-Up
  - 3.2.2 Local
  - 3.2.3 On-Line
- 3.3 System Architecture
  - 3.3.1 CPU Logic
  - 3.3.2 Video Logic
  - 3.3.3 System Communication Logic
  - 3.3.4 Modem Option (VT22X-AA)
  - 3.3.5 Power Supply
  - 3.3.6 Keyboard
  - 3.3.7 Monitor Components
- 3.4 System Interaction
Chapter 4 CPU Logic
- 4.1 General
- 4.2 Major Circuits and Components
  - 4.2.1 Central Processor Unit (CPU)
    - 4.2.1.1 8051 CPU Internal Circuits
    - 4.2.1.2 8051 CPU Transactions
  - 4.2.2 Address Latch
  - 4.2.3 Read Only Memory (ROM)
  - 4.2.4 Data Buffer
  - 4.2.5 Screen RAM
  - 4.2.6 Attribute RAM
  - 4.2.7 Select Decoder
  - 4.2.8 Keyboard Interface (I/F)
  - 4.2.9 Nonvolatile RAM (NVR)
  - 4.2.10 Configuration Register
- 4.3 Signal Descriptions
- 4.4 Schematic Reference Information
Chapter 5 System Communication Logic
- 5.1 General
- 5.2 Major Circuits and Components
  - 5.2.1 Dual Asynchronous Receiver/Transmitter (DUART)
    - 5.2.1.1 2681 DUART Internal Circuits
    - 5.2.1.2 2681 DUART Addresses
    - 5.2.1.3 2681 DUART Timing Diagrams
  - 5.2.2 Host Data Mux
  - 5.2.3 Printer Interface (I/F)
  - 5.2.4 EIA Host Interface (I/F)
  - 5.2.5 20 mA Interface (I/F)
- 5.3 Signal Descriptions
- 5.4 Schematic Reference Information
Chapter 6 Video Logic
- 6.1 General
- 6.2 Major Circuits and Components
  - 6.2.1 CRT Controller
    - 6.2.1.1 9007 VPAC Internal Circuits
    - 6.2.1.2 9007 VPAC Addresses
    - 6.2.1.3 9007 VPAC Transactions
  - 6.2.2 Timing Generator
  - 6.2.3 Blank Circuits
  - 6.2.4 Character Generator
    - 6.2.4.1 Access Mux
    - 6.2.4.2 Line Buffer
    - 6.2.4.3 Character Output Circuit
  - 6.2.5 Attribute Circuits
  - 6.2.6 Video Converter
    - 6.2.6.1 Conversion Control
    - 6.2.6.2 Parallel-to-Serial (P/S) Converter
  - 6.2.7 Video Output
- 6.3 Signal Descriptions
- 6.4 Schematic Reference Information
Chapter 7 Keyboard (LK201)
- 7.1 Introduction
- 7.2 Physical Description
- 7.3 Functional Description
  - 7.3.1 Keyboard Operation Overview
    - 7.3.1.1 Keyboard Scanning
    - 7.3.1.2 Controls of Audio Transducer and Indicators
  - 7.3.2 Keyboard Firmware Functions
    - 7.3.2.1 Functions Not Changed By CPU Instructions
    - 7.3.2.2 Functions Changed By CPU Instructions
    - 7.3.2.3 Firmware Functions Changed By CPU Instructions
- 7.4 Detailed Keyboard Circuit Description
  - 7.4.1 Keyboard Matrix Scanning
  - 7.4.2 Audio Transducer Control Circuit
  - 7.4.3 Indicator (LED) Control Circuit
  - 7.4.4 Keyboard Communication
    - 7.4.4.1 Keyboard Transmit Mode
    - 7.4.4.2 Keyboard Receive Mode
  - 7.4.5 Reset Signal for 8051 Microprocessor
  - 7.4.6 Hardware Keyboard Identification (ID)
  - 7.4.7 Voltage Supplies
- 7.5 Keyboard Programming
  - 7.5.1 Keyboard Layout and Key Identification
  - 7.5.2 Modes
    - 7.5.2.1 Special Considerations Regarding Autorepeat
    - 7.5.2.2 Special Considerations Regarding Down/Up Mode
    - 7.5.2.3 Autorepeat Rates
  - 7.5.3 Keyboard Peripherals
    - 7.5.3.1 Audio
    - 7.5.3.2 Indicators (LEDs)
  - 7.5.4 Keyboard-to-System Module Protocol
    - 7.5.4.1 Keycode Transmission
    - 7.5.4.2 Special Code Transmissions
    - 7.5.4.3 Power-Up Transmission
  - 7.5.5 System Module to Keyboard Protocol
    - 7.5.5.1 Commands
    - 7.5.5.2 Parameters
    - 7.5.5.3 Peripheral Commands
    - 7.5.5.4 Mode Set Commands
  - 7.5.6 Special Considerations
    - 7.5.6.1 Error Handling
    - 7.5.6.2 Keyboard Locked Condition
    - 7.5.6.3 Reserved Code
    - 7.5.6.4 Test Mode
    - 7.5.6.5 Future Expansion
  - 7.5.7 Default Conditions
    - 7.5.7.1 Audio Volume
- 7.6 Specifications
Chapter 8 Monitor Circuits
- 8.1 General
- 8.2 Major Circuits and Components
  - 8.2.1 Video Amplifier (Amp) Circuit
  - 8.2.2 Horizontal Deflection Circuit
    - 8.2.2.1 Horizontal Processor Circuit
    - 8.2.2.2 Horizontal Driver Circuit
    - 8.2.2.3 Horizontal Output Circuit
  - 8.2.3 Flyback Transformer Circuit
  - 8.2.4 Vertical Deflection Circuit
    - 8.2.4.1 Vertical Processor Circuit
    - 8.2.4.2 Vertical Output Circuit
  - 8.2.5 Dynamic Focus
  - 8.2.6 Brightness Control
  - 8.2.7 CRT Device
Chapter 9 Power Supply
- 9.1 General
- 9.2 Major Circuits and Components
  - 9.2.1 AC Input Components
  - 9.2.2 AC Conversion Circuits
    - 9.2.2.1 +12 V Start Up Circuit
    - 9.2.2.2 Input Rectification Circuit
    - 9.2.2.3 DC Output Circuits
    - 9.2.2.4 Overcurrent Protect Circuit
    - 9.2.2.5 Pulse Width Modulator Circuit
  - 9.2.3 DC OK Circuit
  - 9.2.4 DC Input Components
Appendix A Specifications
Appendix B VT220/VT102 Differences
Appendix C Register Bit Values

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VT220 Technical Manual

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