Major Registers M220

This document is a technical schematic for the "Major Registers M220" circuit board, designed by Digital Equipment Corporation in 1967.

The schematic details the logic and circuitry for the M220 unit, including:

• Component Architecture: It utilizes various logic integrated circuits (ICs) such as DEC 7400, 7460, 7453, and 7482 series.
• Operational Functions: The circuit incorporates logic for shift operations (left/right and double shifts), adder functions (Adders 1 through 5), and various register control signals (e.g., AC Enable, MQ Enable, PC Enable, Memory Enable).
• Technical Specifications: The document specifies that unless otherwise noted, pins 7 are ground and pins 14 are +5V. It includes a power distribution section for +5V, a transistor and diode conversion chart, and a comprehensive list of enable signals used to gate data onto the bus.
• Interface: The design includes connections for data addresses and various register inputs (AC2, MQ2, SR2, SC2, etc.) to facilitate data handling and arithmetic operations within the system.