A read write circuit has {HEAD ~ two data lines} {TAIL ~ each} of which is associated with a read circuit 
A read write circuit has { HEAD ~ two data lines } { TAIL ~ each } of which is associated with a read circuit
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH