DJ11 Asynchronous 16-line Multiplexer Maintenance Manual

This document is the Maintenance Manual for the DJ11 Asynchronous 16-Line Multiplexer, published by Digital Equipment Corporation (DEC), with printings ranging from May 1973 to August 1976.

The manual serves as a comprehensive guide for maintenance personnel, detailing the DJ11's functionality, installation, programming, and troubleshooting.

Key aspects covered include:

1. General Description: Explains the DJ11's purpose as a PDP-11 Unibus interface for up to sixteen serial asynchronous communication lines, supporting various baud rates (75-9600), character lengths (5-8 level code), parity, and stop bits. It outlines different hardware options (EIA, TTL, 20mA current loop) and provides detailed specifications.
2. Installation: Guides users through unpacking, inspection, and the installation procedure, including how to configure line parameters (character length, parity, stop code, and independent speeds for 4-line groups) via switches and solderable jumpers on the M7285 Hex Control Board.
3. Programming: Describes the five addressable registers (Control Status Register, Receive Buffer Register, Transmit Control Register, Transmit Buffer Register, and Break Control Status Register) and their bit assignments, along with interrupt vector information.
4. Detailed Description: Provides in-depth explanations of the DJ11's twelve basic functional blocks, such as selection logic, interrupt logic, Universal Asynchronous Receiver/Transmitters (UARTs), the First In/First Out (FI/FO) buffer, clock logic, maintenance mode logic, and various output interfaces. This section delves into the logic discussion of specific components, often referencing external engineering drawings and integrated circuit schematics.
5. Maintenance: Outlines both preventive maintenance (routine checks and diagnostics) and corrective maintenance procedures. It includes detailed diagnostic testing routines for fault isolation, lists recommended spare modules, and specifies required test equipment.
6. Appendices: Features a signal glossary, IC schematics for the integrated circuits used in the DJ11, and information on floating device and vector addresses for communication devices within a PDP-11 system.