The pump down circuit may be configured to generate {HEAD ~ a pump} down signal in response to the pump up {TAIL ~ signal} and the control signal 
The pump down circuit may be configured to generate { HEAD ~ a pump } down signal in response to the pump up { TAIL ~ signal } and the control signal
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH