The Microtronic Phoenix Computer System - A Microtronic Emulator Running the Original Firmware from 1981

Jason T. Jacques: TMS1xxx emulator, prototype hardware design and breadboarding, refined Microtronic firmware dumping, authentic Microtronic firmware emulator running the original Microtronic firmware ROM with a TMS1600 emulator

Decle: TMS1xxx firmware ROM dumping technology, TMS1xxx disassembler, expert technical advisor

Michael A. Wessel: Arduino-based re-implementation of the Microtronic, first round of Microtronic firmware dumping, PCB design, software integration

About

The Microtronic Phoenix represents a quantum leap in Microtronic emulation.

The Microtronic was an educational 4bit single-board computer system, which was released in 1981 by the company Busch Modellbau in West Germany:

Unlike previous hardware emulators of the 1981 Busch 2090 Microtronic Computer System, the Phoenix emulator is the first emulator that is not only a re-implementation of the Microtronic, but actually runs the original TMS1600 firmware from 1981.

This breakthrough was made possible by a collaboration of Decle, Jason T. Jacques and Michael Wessel, referred to as "the team" in the following.

This project is shared with the community to enable others to relive and experience the original 1981 Busch Microtronic Computer System in an as-authentic-as-possible way.

Latest News

• 04-12-2025: All Firmware variants uploaded ("Phoenix", "Neo Only", "Phoenix Only").

• 02-22-2025: "Neo Only" firmware uploaded.

Background & Genesis

The Microtronic is powered by a mask-programmed Texas Instruments 4bit microcontroller, the TMS1600.

Until now, an authentic Microtronic emulator was impossible as the official firmware had been lost to history, and there was no documented procedure for reading out ("dumping") a TMS1600 firmware ROM. Firmware ROMs of related TMS1xxx devices (e.g., the SIMON game, TI calculators, and the Science Fair Microcomputer Trainer) had been retrieved in the past, but the process usually involved destructive die-decapping.

More recently, an alternative to destructive chip decapping was discovered for dumping the ROM of the 1985 Radio Shack Science Fair Microcomputer Trainer. This process utilizes an Arduino for putting the TMS1xxx into the so-called test mode, which then allows download of the firmware ROM over a serial interface.

After a lot of trial-and-error, the team finally succeeded in April 2024 in retrieving the Microtronic firmware ROM, hence opening up the avenue of re-creating the original Microtronic on modern hardware. The process is described here and, much more detailed and technically accurate, here.

After Decle and Michael had succeeded in enabling the TMS1600 test mode (this process was nowhere documented on the Internet back then), and succeeded in downloading a first version of the Microtronic ROM, Jason then took the lead and analyzed and double checked it, corrected some errors by hand (despite all our efforts, the retrieved firmware still contained some ambiguity!), and, for the first time in history, created an ATmega-based breadboard Microtronic running the original firmware on his TMS1xxx emulator!

Jason's work of curating the firmware and his TMS1xxx Microtronic breadboard hardware emulator opened the avenue of recreating a retro-authentic new version of the Microtronic on modern hardware, running the original 1981 firmware ROM on a TMS1600 emulator on an Arduino / ATmega. We are hence calling this new Microtronic hardware emulator the Phoenix.

Phoenix Overview

The Phoenix board uses an ATmega 644P-20U clocked at 20 MHz, a 24LC256 EEPROM, and an 74LS244 in an abundance of pre-caution for connecting the ATmega's GPIOs to the external world of Microtronic INPUT / OUTPUT ports.

The three different Phoenix firmwares are provided as Arduino folders / "sketches". See below for descriptions of these three different variants. The Arduino Legacy IDE IDE 1.8.19 in...