TWU45 Magtape System Manual Jan77

This document is a System Manual for the Digital Equipment Corporation (DEC) TWU45 Magnetic Tape System, designed for use with the PDP-11/70 Central Processor. Published in January 1977, it is intended for Digital Field Service and customer maintenance personnel.

The manual provides a comprehensive overview covering:

1. System and Physical Description:

   • Components: It details the RH70 Massbus Controller, TM02 Magnetic Tape Controller, TU45 Tape Transport(s), and Magtape Transport Adapter (MTA). The system can accommodate up to four RH70 controllers, each supporting up to eight TM02/TU45 systems.
   • Architecture: Describes the various bus interfaces (Unibus for CPU communication, Massbus for high-speed data transfer between RH70 and TM02, and Slave Bus for TM02 to TU45 communication), and its interaction with the PDP-11/70's Cache Memory and Main Memory Bus.
   • Functional Operation: Explains the roles of the RH70 (register access, DMA data path) and the TU45/TM02 (data recording/playback, error detection/correction, tape mark generation, diagnostics).
   • Recording Techniques & Specifications: Covers NRZI and Phase Encoding (PE) methods, including data formats and tape handling precautions. Key specifications include a maximum data transfer rate of 120,000 characters/second, tape speeds of 75 in/sec (read/write) and 250 in/sec (rewind), and packing densities of 800/1600 bpi.

2. Installation and Maintenance:

   • Provides instructions for mechanical and electrical installation of the RH70, TM02, and TU45, including module locations, Massbus and Slave Bus cabling, jumper configurations, and the use of Light-Emitting Diodes (LEDs) for diagnostics.
   • Outlines acceptance procedures using specific DECSPEC diagnostic programs and discusses preventive maintenance.

3. Operation and Programming:

   • Details the TWU45 command repertoire, categorized into data transfer (e.g., Read, Write, Write Check) and non-data transfer (e.g., Rewind, Erase, Space, Write Tape Mark) commands.
   • Provides extensive descriptions of the 16-bit registers used for control, status, and error reporting (e.g., MTCS1, MTWC, MTBA, MTDS, MTER), including their bit assignments and functions.
   • Explains interrupt conditions, termination of data transfers, and offers programming examples for common operations.
   • Includes a "Suggested Error Recovery" section with procedures for handling various drive or controller errors.

The document serves as a comprehensive guide for understanding, installing, operating, and maintaining the TWU45 Magnetic Tape System.