Other circuitry is coupled to {TAIL ~ system bus} 12 such as {HEAD ~ memory} 17 
Other circuitry is coupled to { TAIL ~ system bus } 12 such as { HEAD ~ memory } 17
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH