motorola 6809

2 Articles

KiCad render of µLind pcb

The 6809 8-Bit Microcomputer: A Father-Son Odyssey

December 6, 2024 by 22 Comments

If you’re nostalgic for the golden age of microprocessors and dream of building your own computer, this story might spark your imagination. [Eric Lind], passionate retro enthusiast and his 14-year-old son, embarked on a mission to craft a microcomputer from scratch, centred around the exotic Motorola 6809 chip: the µLind.

What sets this project apart is its ambition: bridging retro computing with modern enhancements. Starting with just a 6809 and some basic peripherals, the men designed a multi-stage roadmap to realize their dream. Each stage brought new challenges: debugging an address decoder, reworking memory management, and evolving glue logic into programmable GAL chips. Fascinatingly, the project isn’t just about nostalgia—it’s a playground for exploring multitasking operating systems and pushing the boundaries of 8-bit computing.

Their creativity shines in solutions like a C64-compatible joystick port, add-on expansion cards, and a memory overkill of 1MB RAM. With every setback—a missing pull-up resistor or a misrouted IRQ signal—their determination grew stronger. By combining old-school know-how with modern tools like KiCad, they’ve created something that is both personal and profoundly inspiring.

[Eric]’s hope and goal is to establish a community of people that want to expand beyond the traditional Z80 and 6502 based SBC’s. Interested? Read [Eric]’s project log on Hackaday.io and start crafting!

Modern In-Circuit Emulator For The 6809

July 19, 2024 by 12 Comments

The Motorola 6809, released in 1978, was the follow-up to their 6800 from four years earlier. It’s a powerful little chip with many 16-bit features, although it’s an 8-bit micro at heart. Despite its great improvements over the 6800, and even technical superiority over the Z80 and 6502 (hardware multiply, for example!), it never reached the same levels of success that those chips did. However, there are still some famous systems, such as the TRS-80 Colour Computer, which utilized the chip and are still being hacked on today. [Ted] is clearly a fan of the 6809, as he used a Teensy 4.1 to create a cycle-exact, drop-in 6809 emulator!

A small interposer board rearranges the Teensy pinout to match the 6809, as well as translating voltage levels from 3.3V to 5V. With careful design, the Teensy matches the cycle diagrams in the Motorola datasheet precisely, and so should be able to run any applications written for the chip! A great test was booting Extended Colour BASIC for the TRS-80 CoCo 2 and running some test BASIC programs. Any issues with opcode decoding or timing would certainly be exposed while running an interpreted language like BASIC. After this successful test, it was time to let the Teensy’s ARM Cortex-M7 rip and see what it could do.

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