[cctalk] programming the IBM PC synchronous serial boards (Northstar Advantage project)

Did IBM ever publish programming information for their PC SDLC or BiSync communications boards? I’m wondering about the possibility of programming one to drive the synchronous protocol needed for “booting” a Northstar Advantage over its serial port. Or, for that matter, wondering what Northstar had in mind when they made that protocol synchronous - what would they have had driving it? ok bear.