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