The basic transporter was a Motorola synchronous serial interface
chip, a 68xx microcontroller, and a Corvus ASIC. NEC built an integrated
device for them later. The service manuals for some of the early peripheral
controllers described it in detail, unfortunately the only person that
still has that information is Eric Lander, and I have no good contact info
for him any more.
The Macintosh version of the Constellation software just used the SCC
I assume in HDLC mode.