A multiplexer, selectively couples data from either the main memory device or the shadow memory device to an output terminal in {HEAD ~ response} to {TAIL ~ a control signal} 
to
A multiplexer , selectively couples data from either the main memory device or the shadow memory device to an output terminal in { HEAD ~ response } to { TAIL ~ a control signal }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL