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