Tiny8: An Educational 8-bit CPU Simulator with Interactive Visualization

Introduction

Tiny8 is a powerful and educational 8-bit CPU simulator, meticulously crafted in Python. Designed to demystify computer architecture, it provides a hands-on environment for exploring assembly programming and real-time visualization of CPU operations. Inspired by AVR architecture, Tiny8 features a robust 8-bit CPU with 32 general-purpose registers, a comprehensive instruction set, and advanced debugging tools, all without heavy dependencies.

Key features include an interactive terminal debugger with Vim-style navigation, change highlighting, and advanced search capabilities. For visual learners and educators, Tiny8 can generate high-quality GIF/MP4 animations of program execution, illustrating register evolution, memory access patterns, and flag changes. This makes it an excellent tool for understanding how programs interact with hardware at a fundamental level.

Real-time visualization of a bubble sort algorithm executing on Tiny8

Installation

Getting started with Tiny8 is straightforward. You can install it directly using pip:

pip install tiny8

Examples

Tiny8 comes with a variety of examples to help you understand its capabilities. Let's look at a simple Fibonacci sequence calculator.

First, create an assembly file, fibonacci.asm:

; Fibonacci Sequence Calculator
; Calculates the 10th Fibonacci number (F(10) = 55)
; F(0) = 0, F(1) = 1, F(n) = F(n-1) + F(n-2)
;
; Results stored in registers:
; R16 and R17 hold the two most recent Fibonacci numbers

    ldi r16, 0          ; F(0) = 0
    ldi r17, 1          ; F(1) = 1
    ldi r18, 9          ; Counter: 9 more iterations to reach F(10)

loop:
    add r16, r17        ; F(n) = F(n-1) + F(n-2)
    mov r19, r16        ; Save result temporarily
    mov r16, r17        ; Shift: previous = current
    mov r17, r19        ; Shift: current = new result
    dec r18             ; Decrement counter
    brne loop           ; Continue if counter != 0

done:
    jmp done            ; Infinite loop at end

Then, run it using the Tiny8 CLI. You can either use the interactive debugger or generate an animation:

tiny8 fibonacci.asm # Interactive debugger
tiny8 fibonacci.asm -m ani -o fibonacci.gif # Generate animation

Tiny8 also provides a Python API for integrating the simulator into your own scripts:

from tiny8 import CPU, assemble_file

asm = assemble_file("fibonacci.asm")
cpu = CPU()
cpu.load_program(asm)
cpu.run(max_steps=1000)

print(f"Result: R17 = {cpu.read_reg(17)}")  # Final Fibonacci number

Why Use Tiny8?

Tiny8 serves various audiences with its unique blend of simplicity and power:

• For Students: It offers an unparalleled opportunity to write assembly code and observe immediate, visual feedback. Students can understand precisely how each instruction impacts the CPU state, free from high-level abstractions.
• For Educators: Tiny8 facilitates interactive demonstrations, simplifies the creation of assembly programming assignments, and allows for the generation of engaging animations for lectures and teaching materials.
• For Hobbyists: It provides a platform for rapid algorithm prototyping at the hardware level. With minimal overhead and an extensible, readable Python codebase, hobbyists can experiment with low-level programming concepts efficiently.

Links

For more detailed information, documentation, and community engagement, please refer to the official resources:

• Official Documentation: sql-hkr.github.io/tiny8
• GitHub Repository: sql-hkr/tiny8
• Issues: GitHub Issues
• Discussions: GitHub Discussions