Without this firmware the code found in the Arduino IDE would not be compatible with the microcontroller. It is the ICSP header that allows the microcontroller ... This requires to gain some knowledge ...

"Intel and Arduino’s announcement ... known as the Arduino 1.0 pinout). This means that it has 14 digital I/O pins, 6 analog inputs, a serial port, and an ICSP header. "Familiar IDE "The Intel ...

Using such a common header pinout for the Z80 computer allows it to be used with a variety of readily-available Arduino shields. This compatibility is achieved with an analog-digital converter and ...