Meanwhile, using MAME and the real hardware is allowing me to proceed at rapid pace with the PLATOTERM port. It's now connecting out to IRATA.ONLINE, and starting to work smile

https://www.youtube.com/watch?v=e0VZveLqMoY

@OG - It looks like the RS-232-C module is an 8250, just in an odd place...what would it take to hook that up in mame?

-Thom