I integrated the TRS-80 Model I ROMs into my MCLZ8 Z80 emulator and mapped the UART to the TRS-80’s keyboard and video RAM and now have it running on a standalone Teensy 4.1 board!

I am taking advantage of the high-speed USB UART to display the TRS-80 video RAM contents to the user. Whenever something is written to the video RAM, I simply output the complete 64×16 screen contents to the UART! It goes so fast that it looks like smooth motion – similar to flip-book animation.

In theory, it would be easy to map any memory or IO address to the Teensy’s GPIOs so one could write a BASIC program to control some pins on the board and could even implement a parallel bus… I am using the TRS-80 Model I ROMs at the moment. Probably no reason the Model III ROMs wouldn’t work just as well.

One other neat feature is that you can cut and paste a BASIC program into the UART window so you don’t need to type them in! 🙂

Source code is on GitHub: https://github.com/MicroCoreLabs/Projects/tree/master/MCLZ8/Code