I think it's likely the C139/C422 is actually a Fujitsu MB89372, A or B. Both chips look identical and have the same number of pins on each side, 13 by 19 pins. Sega used this in their X and Y link boards and Sailorsat got Power Drift Link Version's comms working. Idk an approach for emulation on this device because I can't find any form of data or manual.