From the limited information published it seems that the ROM is just another butchered DGOS ROM with the FDC drivers replaced with Microfusion Network drivers which interface to two types of network interfaces.
There's a bidirectional serial interface using 2 free pins of the microbee's serial port & provision for an auxilliary parallel port connected device.
The microbee bit bashed serial & tape I/O remains intact.
The keyboard reset & POJ circuit is a bit different with the BOOT ROM being located at %0000. When it boots, it copies the butchered boot ROM image to %E000 and then jumps to it.
Like other microbee boot ROMS the keyboard is scanned during the reset key released but with a few variations:
'B' forces a boot from CIFNet interfaces.
'M' goes to the butchered DGOS monitor
'BRK' execs the program at %8000 (presumably a priorly downloaded MWBASIC image).
If no key is pressed, it then checks its sysinit bytes and if these are not initialised the ROM image (now in RAM) checks the parallel port and if an interface is detected the unit is assigned unit numbers 0-9.
If the unit is not detected, the bottom 5 bits of the onboard DIP switch are read to assign unit numbers '@' through 'X' or '?'.
Be aware that some of the boot ROM variables have been relocated and thus are not 100% compatible with the original microbee Boot ROMs and may cause issues with some programs.
The network boot code is enough to connect to a server, load its network BIOS/drivers and continue executing from %D600.
There's a bidirectional serial interface using 2 free pins of the microbee's serial port & provision for an auxilliary parallel port connected device.
The microbee bit bashed serial & tape I/O remains intact.
The keyboard reset & POJ circuit is a bit different with the BOOT ROM being located at %0000. When it boots, it copies the butchered boot ROM image to %E000 and then jumps to it.
Like other microbee boot ROMS the keyboard is scanned during the reset key released but with a few variations:
'B' forces a boot from CIFNet interfaces.
'M' goes to the butchered DGOS monitor
'BRK' execs the program at %8000 (presumably a priorly downloaded MWBASIC image).
If no key is pressed, it then checks its sysinit bytes and if these are not initialised the ROM image (now in RAM) checks the parallel port and if an interface is detected the unit is assigned unit numbers 0-9.
If the unit is not detected, the bottom 5 bits of the onboard DIP switch are read to assign unit numbers '@' through 'X' or '?'.
Be aware that some of the boot ROM variables have been relocated and thus are not 100% compatible with the original microbee Boot ROMs and may cause issues with some programs.
The network boot code is enough to connect to a server, load its network BIOS/drivers and continue executing from %D600.