ALU_Architecture_Notes.md

ALU Architecture Notes

High-Level Structure

A basic ALU design for Logisim should typically include:

• Input Buses
• Accumulator Register
• Operand Register
• Operation Select Control
• Arithmetic Subcircuits
• Logic Subcircuits
• Shift Subcircuits
• Output Selection Multiplexer
• Output Register

Suggested Internal Blocks

Arithmetic Unit

Handles:

• Addition
• Subtraction
• Multiplication
• Division

Logic Unit

Handles:

• AND
• OR
• XOR
• NOT

Shift Unit

Handles:

• Shift Left
• Shift Right

Control Unit

Maps opcodes to subcircuit selection and output routing.

Multiplexer Layer

Chooses which functional block drives the final output.

Suggested Logisim Build Order

1. Build Input And Output Registers
2. Build Addition And Subtraction
3. Build Logic Operations
4. Build Shift Operations
5. Add Multiplexer-Based Output Selection
6. Connect Control Signals
7. Validate Each Operation One By One

Implementation Note

If the full Logisim circuit is built later, this document should be updated with:

• Subcircuit names
• Bit widths
• Control line definitions
• Screenshots of the final design