Edstrom: regarding the PIT, it would be helpful if the port lines were brought out individually. So you have MCFG_PIT68230_PA0_CB() and then a series of public WRITE_LINE members like rxa_w and friends in z80scc.
Since there is no way I can see to send TIN to the PIT and the PIT doesn't ever output H4, that means I *am* actually stuck on it. I've committed a revised micro20.cpp that makes the lack of those things obvious and testable, good luck
