Maindec 712

This document describes Maindec 712, a diagnostic program designed to test the functions of the PDP-7 paper tape punch. The program consists of three distinct parts, all residing in memory simultaneously, allowing the operator to switch between them.

1. Startup Delay Test (Part 1): This test verifies the 1-second delay required for the punch's drive mechanism to engage after the initial Punch Select IOT (Input/Output Transfer) instruction is given. It checks if the punch flag is set prematurely.
2. Scope Waveform Test (Part 2): Intended for use with a Cathode Ray Tube (CRT), this program continuously punches the contents of the Accumulator (AC) Switches onto tape in either binary or alphanumeric modes. It allows for visual inspection of character spacing, detection of overlapping characters, and examination of punch waveforms, as well as testing for residual noise by punching characters and their complements.
3. Random Sequence Punch (Part 3): This section generates and punches a sequence of pseudo-random numbers onto a tape. The generated tape is then read back and checked against the expected sequence, allowing for the detection of errors like spurious bits or effects of residual noise on adjacent channels.

The document details the memory and equipment requirements (standard PDP-7 with paper tape reader and punch), specific loading and operating instructions, various AC switch settings to control test parameters (e.g., punch mode, error halting, message printing), and a comprehensive list of error messages with their causes and recovery procedures. It also includes a partial program listing for Maindec 712. Part 1 has a specific execution time of just over one second, while Parts 2 and 3 can run indefinitely.