TM11

This document is an Engineering Change Order Log from Digital Equipment Corporation, detailing hardware and documentation updates for the PDP-11 Family, specifically concerning the TM11/TU10 Magtape Control unit. Issued between May 1972 and May 1973, it records various problems and their corresponding corrections, primarily addressing:

1. Wiring and Circuitry Issues: Correcting inaccurate signal names, pin assignments, and signal gating logic to resolve problems like noisy signals, system hangs under DOS, and improper magtape select line behavior.
2. Documentation Discrepancies: Extensive updates to various documents including wire lists, accessory lists, software lists, module schematics, master drawing lists, installation procedures, and engineering prints to accurately reflect current hardware configurations and system behavior, including physical component relocation.
3. Magtape Control Logic: Fixing specific problems related to CRC error handling during tape operations (read, write, space) and ensuring the correct generation of control signals like CONTROL INITIALIZE (CINIT) based on tape movement (e.g., backspacing).
4. Installation and Effectivity: Correcting inaccurate effectivity dates and specifying the use of magtape diagnostics in installation and test procedures for previous Field Change Orders.

Many of these changes required immediate in-plant rework and field retrofits for existing TM11 units.