M716

This document is a schematic diagram for the Digital Equipment Corporation (DEC) M716 control circuit for a CR 81 component, dated 1968.

Key features and components:

• Proprietary Nature: The schematic is proprietary to DEC, intended solely for test and maintenance purposes.
• Input/Output: It processes various "I/O Bus In" signals (IN 0 through IN 11) using a network of digital logic gates and generates multiple "ZONE" outputs (ZONE 0 through ZONE 12), each with an associated index.

• Integrated Circuits: The core logic is implemented using a variety of DEC74xx series integrated circuits, including:

  • DEC7401N (for E1, E5, E7, E13, E15)
  • DEC7474N (for E2, E4, E6, E8, E11, E14 - likely flip-flops or registers)
  • DEC7400N (for E3, E9, E17 - likely NAND gates)
  • DEC7420N (for E10)
  • DEC7430N (for E12)
  • DEC7440N (for E16)

• Discrete Components: It includes standard resistors (220Ω, 470Ω), diodes, and various capacitors (e.g., 6.8µF, 560pF, 0.1µF) for power conditioning, filtering, and timing.

• Control Signals: Features "IOT 634", "IOT 632", and an "INITIALIZE" input (BS2).
• Test Points: Multiple test points (BV1, AD1, BV2, BU2) are provided for diagnostics.
• Power Supply: Connections for +5V and Ground (GND) are indicated.

In essence, it's a detailed digital logic circuit diagram from the late 1960s, showing the interconnections of standard TTL-era integrated circuits and discrete components to manage control functions for a specific hardware unit, the CR 81.