M7821

This document, "DCS M7821-0-1," provides a comprehensive technical description of the "INTERRUPT CONTROL M7821" module, developed by Digital Corporation.

It consists of two main parts:

1. Page 1 (Parts Reference, Notes, Component Placement):

   • Parts Reference: Lists the Bill of Materials (BOM), including various integrated circuits (primarily TTL logic, such as 74xx series and 8881), capacitors (e.g., 330pF, 6.8uF, 0.1uF), and resistors.
   • Notes: Provides critical information for assembly and configuration, such as instructions for setting "VECTOR BIT JUMPERS," the use of the "NPR JUMPER (W9)" specifically for some PDP-11 processors, standard pinouts for GND and +5V, and default component values (resistance in ohms, capacitance in picofarads, 0.1mfd for un-noted capacitors).
   • Component Placement: Features a diagram showing the physical layout of all components on the circuit board, including ICs, capacitors, resistors, and various jumpers (W1-W9).

2. Page 2 (Schematic Diagram):

   • Presents a detailed logic schematic of the Interrupt Control module. It illustrates the interconnections of the various ICs using standard logic gates (AND, OR, NAND, NOR, D-type flip-flops, buffers) to implement the interrupt control functionality.
   • The schematic includes specific signals related to bus operations, such as "A/B REQUEST," "GRANT," "BUS A/B BG IN/OUT," "NPR," "BBSY," "SACK," and various "INTR DONE" signals, indicating its role in managing interrupt requests and responses within a computer bus system (likely for a PDP-11 based system, as suggested by the notes).

In summary, the document serves as a complete technical specification for the M7821 interrupt control board, covering its components, physical layout, assembly instructions, and detailed electrical logic.