Loop prevention indicators

           8  7  6  5  4  3  2  1
        1  H  G  F  E  D  C  B  A

        A               Type
        0               request
        1               response
        If bit A equals to 0 (request):
        bits H-B        Spare
        If bit A equals to 1 (response):
        bits
        C B             Response indicator
        0 0             insufficient information (note)
        0 1             no loop exists
        1 0             simultaneous transfer
        1 1             spare
        bits H-D        Spare
        NOTE - The value "insufficient information" may be received due to interworking.