Simple 16-bit CPU in Digital

Overview

This is a simple 16-bit CPU implementation built using Digital, a digital circuit simulator. The current version implements basic functionality to add two numbers and store the result in a register.

Features

• 16-bit data bus
• 4 general-purpose registers (R0-R3)
• Basic arithmetic operations (currently only addition)
• Program counter for instruction sequencing
• 32-bit instruction format

Current Implementation

The CPU currently supports:

• Loading values from input into registers
• Adding two register values
• Storing results back to registers

Instruction Set Example

The EEPROM contains sample instructions:

• 3004d1 - Load immediate value into register
• 1001f - Add operation
• 23001f - Store operation
• 12001f - Additional operations

How to Use

1. Open the circuit in Digital
2. Set input values:
   • Port A: 16-bit input value
   • Port SD: 8-bit instruction data
3. Use the clock button to step through instructions
4. View results in the output registers R0-R3

Inspiration

This project was inspired by Ben Eater's 8-bit computer and various educational CPU design videos found online. The design incorporates concepts from these resources while adapting them to the Digital environment.

Future Improvements

• Implement more ALU operations (subtraction, logical ops)
• Add memory access instructions
• Improve instruction decoding
• Add conditional branching

Requirements

• Digital Circuit Simulator