VT11 Graphic Display Processor

The VT11 Graphic Display Processor, developed by Digital Equipment Corporation (DEC), is a high-performance peripheral for PDP-11 series computers, connecting via the Unibus. It functions as a Direct Memory Access (DMA) device, independently fetching and executing display programs from memory and communicating with the CPU through Non-Processor Requests (NPRs) and interrupts.

Key features and functionalities include:

• Graphics Generation: Capable of generating various elements on VR14 or VR17 CRT displays, including:

  • Vectors: Digitally calculated with automatic end-point updates to prevent drift, offering solid, long dash, short dash, and dot-dash line types.
  • Characters: A comprehensive character set (96 ASCII, 31 special) with upper/lower case, correct descender positioning, and italics, generated from a 6x8 dot matrix.
  • Points and Graphplots: For displaying individual points and automating X/Y axis plotting.

• Display Characteristics: The display is automatically refreshing for a bright, continuous image, features a hardware blink function, and provides eight programmable intensity levels.

• User Interaction: Supports a 375 Light Pen for direct operator-processor interaction.
• Design & Hardware: Comprised of three main hex-height modules (M7013 for timing/control/decode, M7014YA for Unibus/address control, A320 for vector/character generation and analog circuits). Its hybrid digital and analog design contributes to stability and minimal adjustment requirements.
• Programming Interface: Utilizes a 16-bit instruction word length, supporting five control instructions and six data formats for efficient display program execution.

The manual also covers the theory of operation, maintenance adjustments, diagnostic programs, and troubleshooting procedures for the VT11.