M4 Board, z80 rom part
Once M4ROM.BIN has been assembled, it can be place in the root of the microSD card and it will be loaded instead of the ROM embedded in the firmware. Use this for your own custom builds.
Information about the various commands that interface to the board can be found here: http://www.spinpoint.org/cpc/m4info.txt
General information about M4 board can be found here: http://www.spinpoint.org