VT11 Graphic Display Processor

The VT11 Graphic Display Processor is a high-performance display processing unit (DPU) designed to operate as a peripheral for PDP-11 series computers. It functions as a Direct Memory Accessing (DMA) device, allowing it to independently fetch and execute display programs from memory using Unibus Non-Processor Requests (NPRs).

The VT11 uses a blend of digital and analog techniques to ensure stable operation with minimal adjustments, preventing accumulated errors or drift in beam position. Key features include an efficient vector function, supporting four line types (solid, long dash, short dash, and dot-dash), with digitally calculated endpoint updates. Its character generator offers a comprehensive set of 96 ASCII and 31 special characters, including upper and lower case, descender logic, and the ability to display characters in italics across eight intensity levels. The display is automatically refreshing, providing a bright, continuous image. The processor's instruction set, comprising five control instructions and six data formats, enables versatile display programming, including an automatic graph/plot feature. It is compatible with VR14 or VR17 CRT displays and supports operator interaction via a 375 Light Pen.

The VT11's hardware is modular, utilizing M7013 (timing, character control), M7014YA (Unibus interface, vector control), and A320 (vector/character generators, digital-to-analog converters) modules. The manual provides detailed information on its theory of operation, diagnostic programming, and maintenance procedures.