INT 21 - Brian Antoine Seagate ST-01 SCSI.SYS - IOCTL - EXECUTE COMMANDS
        AX = 4403h
        BX = handle for device "SCSITAPE"
        CX = number of bytes to write
        DS:DX -> SCSITAPE control block (see below)
Return: CF clear if successful
            AX = number of bytes actually written
        CF set on error
            AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: INT 78/AH=10h

Format of SCSITAPE control block:
Offset  Size    Description
 00h    WORD    command type
                'F' Format (argument 1 = interleave, argument 2 = format type)
                'E' Erase
                'R' Rewind
                'L' Load
                'N' No Load
                'S' Space (argument 1 = count, argument 2 = type)
                'M' File Mark (argument 1 = count)
                'A' Reassign
 02h    WORD    argument 1
 04h    WORD    argument 2
 06h    WORD    segment of command buffer
 08h    WORD    offset of command buffer
 0Ah    WORD    length of command buffer