FFT Frequency Range

Ok, I think I have the ADC and FFT clocks working correctly, but I am still having issues syncing them with SignalTap. If I use a PLL block, SignalTap doesn't recognize it as an available clock. If I use a clock_derived block and use it for SignalTap, then SignalTap never stops collecting data; when I click "Acquire," SignalTap just freezes and I have to force quit Matlab. How do you suggest I slow down the SignalTap data acquisition so it is in sync with the FFT output data? Sorry to keep bugging you, but I feel like I'm getting close to making this thing work.