It uses the serial port. I seem to remember utilities
for
the PC that pretend to be a disk drive for an M100 in this
fashion, as well as tools that would let the drive connect
to the PC. I think the drive came with a disk containing
a utility or two.
TS-DOS, available from Club 100, can be either disk or ROM based.
Desklink, available on the Club 100 web site as 'DL-ARC.EXE', also includes
limited RAM based versions that can be transferred to the 100/102 using a
null modem cable. The Desklink archive is what I use to turn my 486 laptop
or Mac clone into a fileserver for my Model 102. Once you use Desklink to
transfer the RAM-based TS-DOS loader into the 100/102, you should then be
able to access the portable disk drive.
Jeff