I found an interesting project on the Internet of a Z80 processor on a breadboard that was connected with wires to an Arduino Mega board. It had some code with it, it was far from complete but it triggered me. I adopted the idea and improved it, rewrote the Arduino code and improved the hardware design. The Z80 processor in this project is running at 200 Khz, clocked from the Arduino and the Arduino emulates 8 kb of ROM and 6 kb of RAM and serial input and output. With this simple and cheap configuration you have a complete working Z80 based computer. With some adjustments I even got a complete Basic interpreter running on this hardware with the serial I/O of the Arduino as interface. But it is also nice to write your own assembler code and see it not only running in an emulator, but also on a real Z80 processor. Just put your generated HEX code in the memory.h file and recompile the Arduino sketch and upload it to the Mega board. On reset the Z80 will execute the code in the ROM section of the MEGA. Have fun!
https://www.heinpragt-software.com/software_development/z80_arduino_mega_project.html
