Mass Storage Control Protocol
From Computer History Wiki
Mass Storage Control Protocol (usually MSCP; sometimes given as Tape Mass Storage Control Protocol, TMSCP, when magnetic tape is involved) was a relatively sophisticated host device controller/CPU interface protocol used by DEC to interact with disks and magnetic tape drives for, amongst other computers, PDP-11s and VAXen.
It ran over a number of different lower layers for the physical connection to the drive(s), including Standard Disk Interconnect, Low End System Interconnect, and Digital Storage Systems Interconnect.