Microtape Manual

XXOID:

This document is a technical manual for the Digital Equipment Corporation (DEC) Microtape system, consisting of the Type 550 Microtape Control Unit and the Type 555 Dual Microtape Transport.

The manual provides a system overview, detailing the Microtape's capabilities as a fast, flexible, and portable magnetic tape storage device compatible with PDP-1 and PDP-4 computers. Key sections include:

• System Summary: Explains that Microtape acts as a program-break control device that allows for word-by-word data transfer, rather than block transfers, facilitating bidirectional reading and writing.
• Operating Instructions: Covers loading procedures for tape and the transport, as well as an explanation of manual switch functions.
• Programming: Details how the system interacts with the computer, including modes of operation (Search, Read, Write, and Move) and the use of subroutines (Microtog and Microtrieve) for maintenance, diagnostics, and data storage/retrieval.
• Theory of Operation: Provides a technical breakdown of the engineering design, covering the timing and mark tracks, the window register, and how the control unit manages data transfers.
• Maintenance: Outlines preventive maintenance (cleaning and visual inspection) and corrective maintenance (troubleshooting random errors, adjustments of stop time, and circuit testing).
• Pertinent Documents: Lists related publications and library programs available for the system.

The document includes a block diagram (Figure 1) of the Tape Control 550 and detailed instruction lists for PDP-1 and PDP-4 integration.