This is a simple interface to the DEC RX01 floppy disk unit, which is part of the console LSI-11 subsystem for VAX-11/780s. Access is given to the entire floppy consisting of 77 tracks of 26 sectors of 128 bytes.
All I/O is raw; the seek addresses in raw transfers should be a multiple of 128 bytes and a multiple of 128 bytes should be transferred, as in other “raw” disk interfaces.