TC01 TU55 overview

This document describes the DECtape system, specifically the TU55 magnetic tape transport and the TC01 control unit, as a fast, convenient, reliable, and low-cost input/output data storage and updating facility.

Key features and functionalities include:

1. TU55 Transport: A bidirectional magnetic-tape drive designed for minimal maintenance and wear, featuring direct-drive motors, no capstans or pressure pads, and electromagnetic braking. It uses pocket-size reels with a capacity of up to 3 million bits (equivalent to 4,000 feet of paper tape) and operates at 97 inches per second.
2. TC01 Control: This unit interfaces up to eight TU55 transports with a PDP-8 computer, handling the transfer of 12-bit binary information. It employs redundant, phase recording for high reliability and uses prerecorded timing and mark tracks to simplify programming by enabling fixed position addressing and block/word addressability.
3. System Operation: The system supports selective updating, automatic word transfers for concurrent processing (at 15 kc character rate), and bidirectional data access. Data is stored in flexible block formats, separated by control words rather than inter-record gaps, maximizing storage capacity. Error detection is performed using checksums.
4. Software Support: DEC provides subroutines for data storage, retrieval, and diagnostics. A DECtape Library System allows users to manage programs on tape, while specific programs (like DECTOG) facilitate tape formatting, error checking, and maintenance.
5. Control Modes: Various modes are available for tape movement and data transfer, including Normal Mode (tape format controlled), Continuous Mode (word count register controlled), Search, Read Data, and Write Data, along with functions for writing timing and mark tracks.

The document also provides detailed specifications for the physical dimensions, power requirements, and performance characteristics of both the TU55 and TC01, as well as cabinet installation guidelines.