The Omnibus Interface

This document, titled "The Omnibus Interface," serves as Chapter 9 of the PDP-8/E documentation. It provides comprehensive technical guidance for users attempting to design their own interface control modules for the PDP-8/E computer's OMNIBUS architecture.

Key contents include: * OMNIBUS Description: An overview of the physical structure and backplane connectors, which eliminates random wiring and supports 20 modules per assembly. * Bus Specifications: Logic levels, systems configuration, and bus loading rules. * Data Transfer Methods: Detailed explanations of Programmed I/O Transfers, the Interrupt Facility, and Data Break Transfers (including one-cycle and three-cycle data breaks). * Signal Definitions: Extensive tables defining OMNIBUS signals for programmed I/O, data breaks, and basic system control, including timing diagrams. * Design & Construction: Guidelines for building custom interfaces, including component layout, grounding strategies, cabling suggestions, and timing criteria to avoid bus contention or propagation issues. * Expansion: Information on integrating peripherals via the External Bus and utilizing M-Series logic modules to build custom interface hardware.