dist30

This document outlines the DIST30 MACRO-V36 assembly language routines, developed in 1969 for Digital Equipment Corporation's (DEC) Type 30 Display (interfaced with a Type 348) or, alternatively, a Type 340 Display, configurable via a T30 switch.

The core function of these routines is to manage display operations by handling interrupts from the display data channel, processing user-defined command pointer lists, and outputting data sections via the BLKO command. Key functionalities include:

• Display Control: Routines like DISNXT (advances display from command list), DISFIN (manages end of display blocks), OVT2 (handles command list completion and restart logic), DISBEG (initializes new display sequences), and DISOUT (main output UUO handler, marks device active) collectively manage the display's state and data flow.
• Interrupt and Input Processing: PENINT processes non-data channel interrupts (e.g., light pen), CLOK handles clock-level requests for display restarts, and DISIN provides rudimentary light pen input handling.
• Error Handling and Shutdown: DISINI deactivates the display and handles shutdown conditions, while ADRER specifically addresses memory protection violations during data processing.
• Data Integrity: The system validates all addresses in the command list against user memory areas to prevent invalid memory references.