GT40/GT42

This document provides comprehensive instructions and specifications for the GT40 and GT42 Graphic Display Terminals, which operate via a PDP-11/10 computer. It includes:

• System Description: Details on hardware organization, including the CPU, Display Processor (DPU), memory, and peripherals.
• Start-up & Operation: Procedures for starting the terminals in various system configurations (terminal systems, paper tape systems).
• Specifications: Technical specifications for the display processor, communications interface (DL11), core memory (MM11), keyboard (LK40), and CRT monitor.
• Interfacing: Overview of the Unibus structure and parallel port, and detailed DL11 serial port programming.
• Programming: Concepts for both the CPU and DPU, including instructions, important registers, and programming examples.
• Advanced Techniques: Information on subroutines, light pen interaction, and specific programming restrictions (e.g., flicker control).
• Bootstrap Information: Descriptions and source code listings for the communications bootstrap ROM.