> I am considering adding rs232 ports to this driver to enable linking for this > hardware. What I need to find out is if there is any special device/hardware/chip > that makes these games communicate. Race Drivin uses a SCC68681 dual asynchronous > reciever/transmitter (DUART) which I don't see something like this on a Midway V-Unit > pcb. > > In fact...these V-Unit games have to use some form of DUART. I can prove this from a > failed attempt to link two Cruis'n USAs with crap LCD monitors (game sends garbage > data the other pcb(s) can't read). If only this wasn't missed.
Communication between two machines is through a parallel interface. See schematic sheet 18/25, or page 70 of this pdf: