I have been using SCO Unix and Digiboards for many years (over 15 ) and I am running into a problem that appears to be specific to Digiboard ports on SCO Openserver 6.0. I have tried this on 3 different 6.0 systems and with two different Digiboard types (PC-Xem and 920xr). I've downloaded MPI 4.2.5 in my latest tests.
What happens is if I try to do a "cu" to a Digiboard port, it quits right away and gives me a "Lost Carrier" message. I have Devices set up the usual way (Direct ttyr1a - 9600 direct) but it just won't stay connected. It does seem to work ok with the built-in Com ports (tty1a, tty2a) but not the Digi ports.
This has always worked fine with previous versions of Openserver, up to and including 5.0.7.