The second voltage forms {TAIL ~ a second write current} for a second duration through the resistive sense memory cell in {HEAD ~ a second direction} 
The second voltage forms { TAIL ~ a second write current } for a second duration through the resistive sense memory cell in { HEAD ~ a second direction }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD