Decmate System Architecture Manual

This document is a comprehensive technical reference manual for the DECmate system, specifically focused on the assembly language programming of the VT278 intelligent video terminal.

Key sections of the manual include:

• System Overview: An introduction to the modular hardware components of the DECmate, including the 6120 microprocessor, memory organization, standard peripheral interfaces, and optional expansion modules (such as the DP278 communications option and RL278 disk subsystem).
• Operating Procedures: Detailed instructions on system initialization, power-up self-tests, SET-UP mode navigation, and terminal communication modes.
• Programming: A technical breakdown of the VT278 instruction set, which is an enhanced version of the PDP-8A architecture. This includes detailed information on registers (Accumulator, Program Counter, Link, etc.), memory reference instructions, operate instructions, and I/O transfer instructions.
• Peripheral Programming: Extensive technical guidance on programming standard I/O devices—such as the keyboard/display, printer port, real-time clock, and floppy disk subsystem—as well as the optional communications and cartridge disk controllers.
• Technical Appendices: Reference materials including ASCII/graphic character sets, foreign language keyboard layouts, and detailed electrical/environmental specifications for the hardware components.

The manual is intended for users familiar with programming and assembly language, providing the necessary low-level interface details required to develop or modify software for the DECmate platform.