INT 78 - TARGA.DEV - SEND SCSI COMMAND, RECEIVE DATA (DMA)
        AH = 13h
        DS:SI -> command bytes
        ES:BX -> data storage area
        DX:CX = number of data bytes to transfer
Return: AH = SCSI status byte (if early return mode is clear)
        CF clear if successful
            AL = SCSI message byte (if early return mode is clear)
        CF set on error
            AL = error code (see AH=00h)
Note:   this command receives data using DMA
SeeAlso: AH=12h

Format of SCSI Command:
Offset  Size    Description
 00h    BYTE    length of command
 01h    ???     command bytes