{HEAD ~ a second logic unit} which logically operates the first data and the second transfer control signal, and outputs {TAIL ~ the result} of the logical operation; and 
outputs
{ HEAD ~ a second logic unit } which logically operates the first data and the second transfer control signal , and outputs { TAIL ~ the result } of the logical operation ; and
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH