TU58 DECtape II

This user guide provides comprehensive information for the installation, operation, and programming of the TU58 DECtape II, a low-cost, random-access, fixed-length-block, mass-storage tape system.

The TU58 utilizes preformatted tape cartridges, each storing 262 kilobytes of data in 512-byte blocks across two tracks. Its design emphasizes mechanical simplicity and reliability, controlled by a microprocessor (µP) on a single circuit board, which handles tape positioning, error retry, and communication management, thereby offloading the host system. Communication between the host and controller occurs via Radial Serial Protocol (RSP) or Modified RSP (MRSP), using specific command and data packets with checksums.

The document details the system's specifications, including performance metrics (e.g., 9.3 seconds average access time, 24 Kbits/s data transfer rate), electrical requirements, mechanical dimensions for various configurations (rackmount, tabletop), and environmental operating limits. Different TU58 configurations (e.g., TU58-CA, -DA, -EA, -EB, -VA) are outlined, along with their included components. Digital Equipment Corporation's repair services are also listed.

Operational guidelines cover front panel controls, run indicators, and power procedures for different TU58 versions. Critical instructions for cartridge loading, unloading, and care are provided, including the use of a write-protect tab. Routine maintenance focuses on cleaning the head and motor puck to prevent errors and extend cartridge life, with a trouble isolation table for common issues.

For programming, the guide explains the TU58's high-level instruction set, communication protocols (RSP/MRSP) and packet formats, including various command opcodes (Read, Write, Position, Diagnose) and success codes returned in end packets. Pseudo-Pascal algorithms for basic device handler functions (tudiagnose, tuseek, turead, tuwrite) are included to illustrate programming logic.

Installation procedures are thoroughly described for rackmount and tabletop versions, covering power selection, fuse installation, and accessing the controller board. It also details interface standards selection (RS-422, RS-423/RS-232-C) and jumper configurations for baud rates and interface types. An operational checkout procedure is provided for verifying the interface and drive command functions.

Optional features, such as a run indicator and a boot switch for interfacing with LSI-11 ODT keyboard interpreters, are also discussed. Appendices offer a PDP-11 bootstrap, RSP sequences, sample device handlers, cartridge repair instructions, and a list of field-replaceable unit spares.