Originally Posted By etabeta78
yeah, it seems the board had some sort of serial connection. its emulation is probably beyond my current set of skills, though (my frustration with MegaDrive serial EEPROMs exposed that I clearly suck at understanding serial comms from the running code), so if you want to take a look, the relevant slot device is at src/mess/machine/sns_event.c
We'd probably need a dump of the mcu prom ( which looks like it'd be possible) because as Logan says, I don't actually know what it does or if it's even a serial port.