新手求教

请问遇到如下错误该怎么办？？
           A reference voltage has not been detected on the ribbon cable
        interface to the target system ( pin 2 ).  Check that power is applied
         to the target system and that the ribbon cable is properly seated at
         both ends.  The status LED on Platform Cable USB will be GREEN if target
         voltage is in the proper range and applied to the correct pin.