There are few ways to accomplish this...
one is the PLL, it takes its signal from a voltage controled oscillator VCO the voltage that controls it goes to pin 9 its from 1v to vcc-1... the frequency is determined by the capacitor and resistor relation, it also allow you to have an offset of the fequency such that the band where it can lock can be varied... i think this is R2 going into pin 12... pin 11 goes R1 and pins 6 and 7 goes the capacitor... the resistors or pots terminate in ground 0v.. the frequency is independent therefore meaning it oscillates disregard of its in resonance or not.. the frequency going out also gets into the pll phase comparator... the phase comparator works on edge detection. you also need a feedback from where you take the signal to compare with on the other input of the phase comparator... the output of the phase comparator is filtered and feedback into the pin 9 VCO... the phase comparator will charge up or discharge the filter capacitor accordingly with phases diferences creating a phase locked loop... the loop may have delay on the feedback side that may need to be compensated for geting proper absolute perfect resonance..
is important that you understand the phase relations of the pulse you are applying and how you get the feedback... the feedback signal must come from what you are trying to resonate.. depending on the coupling method etc...
