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