Digital Computer Option 550 Micro-Magnetic Tape Control

Summary

This document provides technical information and operating procedures for the Digital Equipment Corporation 550 Micro-Magnetic Tape Control. It outlines the system’s ability to control up to four 555 dual tape transports (eight drives) for the PDP-1 and PDP-4 computers. Key aspects covered in the document include:

• System Overview: Describes how the control handles data transfers, assembly/disassembly of words, tape formatting via a Mark Track, and timing functions.
• Operational Mechanics: Explains control actions for reading, writing, and searching, including flag signaling, error detection via checksums, and timing delays associated with tape movement and stop/start commands.
• Instruction List: Provides specific PDP-4 code instructions for reading, writing, loading the control, selecting units, reading status, and testing flags.
• Transfer Operation & Timing: Details the specific timing restrictions required for reliable operation of the 555 tape transport, emphasizing that commands must be held for specified durations to allow relays to react.
• Troubleshooting & Field Service: Includes technical tips regarding electrical noise (dampening diodes), grounding requirements for motors/chassis, and known issues with hub alignment and skew.
• Diagnostic Programs: Outlines several programs used for testing and maintenance, including:
  • Micro Tape Data Test: For checking data transfer integrity.
  • Micro Tape Dump and Retrieve: For storing and retrieving information.
  • Micro Tape Exciser: For testing tape in multiple or individual block modes.
  • Micro Tape Format Pack: For writing mark tracks, timing tracks, and block numbers.
  • Micro Tape Rocker Program: For oscillating tape for debugging purposes.