LGCmaintIntro

This document describes various aspects of DECsystem-10/PDP-11 computer systems, focusing primarily on maintenance software and fundamental digital logic troubleshooting.

The document is broadly structured into three main sections:

1. DECsystem-10/PDP-11 System Architecture:

   • Includes block diagrams illustrating the interconnection of hardware components like the KL10 Central Processor, DTEs (Data Terminal Equipment), User/Remote Terminals, Unibus, Massbus, and various I/O devices (disk, tape, memory modules like MF11-UP, MM11-UP, and ROM modules like BM873).
   • Describes typical device controllers, their selection networks, interrupt assignments, and operational flags (busy, done).
   • Details machine instructions for memory and I/O operations.
   • Explains the Console Processor Subsystem, which uses a PDP-11 minicomputer (KD11-A CPU, KY11-D console, MF11-UP/MM11-UP memory) to provide bootstrap, console command facilities, and interface with the KL10 CPU via the DTE20. It also covers I/O interfaces (DL11-C/E, LA36 terminal), disk systems (RJP04/06, RH11), and magnetic tape systems (TC11-G, TU56).

2. Maintenance Software:

   • General Description and Use: Defines maintenance software as programs to determine hardware operational status, used throughout the product lifecycle (design, manufacturing, installation, acceptance, preventive, and corrective maintenance).
   • Maintenance Libraries: Organized by the base processor executing the programs and the type of system maintained. Three main libraries are described:
     • 11-Based 11 Maintenance Library: Written in PDP-11 machine language to diagnose PDP-11 systems. Includes utilities like XXDP (diagnostic monitor), XTECO (editor), UPD (updater), and COPY. Features a modular DECX/11 system exerciser.
     • 11-Based 10 Maintenance Library: Written in PDP-11 machine language, executed by the KL10 console front-end to diagnose KL10 processor, main memory, and channels. Key component is KLDCP (Diagnostic Console Program), which handles loading, command processing, and error handling. Other utilities include KLDCPU, MEMCON, and TRACON. Focuses on hardware (FRU) tests, using TIC files and isolation routines for fault isolation and calculating fault confidence.
     • 10-Based 10 Maintenance Library: Written in PDP-10 machine language for PDP-10 processor, storage, and I/O subsystems. Utilities include DIAMON/D20MON/MAGMON (diagnostic monitors), MAGTAP, KLAD10, DDT (debugger), and SUBRTN. Discusses running diagnostics in user versus executive mode, with the operating system often acting as a system exerciser.
   • Components of Maintenance Libraries:
     • Utility Programs: Bootstrap loaders, downline loaders, diagnostic monitors, program/file maintenance utilities, and hardware utilities.
     • Control Files: ASCII text files for automating sequences of diagnostic commands.
     • Diagnostic Programs: Categorized into Operability Tests (detect solid faults, including Hardware/FRU tests and Functional tests) and Exercisers (detect intermittent faults, including Subsystem and System exercisers, testing reliability and interaction).
   • Diagnostic Program Control and Structure: Operational control through console switches and operator dialogue. Internal structure comprises initialization, main diagnostic segment, service routines, and data storage. Detailed fault handling procedures, including fault convergence and fault confidence calculation for intermittent errors, are explained with case studies and flowcharts (e.g., DIACON).

3. Digital Logic (ECL and TTL) Waveforms and Troubleshooting:

   • Emitter-Coupled Logic (ECL):
     • Introduction: Discusses ECL features (high speed, non-saturating transistors, low power, large fanout) and basic circuit theory (differential amplifier, emitter-follower outputs).
     • Basic Transmission Line Theory: Explains signal reflections, impedance mismatch, and termination methods (series, parallel) to prevent "ringing" in high-speed circuits.
     • Troubleshooting Guide: Provides typical fault waveforms and explanations for common ECL problems (unterminated lines, shorts to -2V, improper termination, capacitor in signal path, shorted complementary outputs, open input etches, signal shorted to ground, two shorted signals).
     • Logic Symbology: Includes datasheets with pinouts, function select tables, truth tables, and descriptions for various ECL integrated circuits (e.g., counters, shift registers, RAMs, ALUs, multiplexers, decoders, flip-flops).
   • Transistor-Transistor Logic (TTL):
     • Troubleshooting Guide: Similar to ECL, provides fault waveforms and explanations for common TTL issues (open collector output with no termination, open input etches, two shorted signals, capacitor in signal path, signals shorted to ground or +5V).
     • Logic Symbology: Includes datasheets for various TTL integrated circuits (e.g., data selectors/multiplexers, J-K master-slave flip-flops, RAMs, priority encoders, ALUs).