M159 4-Bit Arithmetic Logic Unit

Summary The M159 4-Bit Arithmetic Logic Unit (ALU) module is a hardware component built around a single DEC74181 integrated circuit. Nine of these modules are utilized within the FP15 Floating-Point Processor to facilitate 36-bit arithmetic and logic operations.

Key features include:

• Operational Flexibility: The unit performs various arithmetic operations and logic functions based on the settings of its MODE control and function select inputs (S0–S3).
• Truth Table: The document provides a specific truth table detailing the required input states for two arithmetic functions (A+B and A-B-1) and five logic functions (A, -A, B, -B, and Logical 0).
• Advanced Capabilities: The module includes an A=B comparator output for equality checking and supports full carry look-ahead for high-speed carry generation.
• Electrical Specs: Each input represents a 1-unit load, and outputs are capable of driving 10-unit loads.