Description
If you remove the input clock to a PLL in a Stratix® - series, Cyclone® - series, or Arria® GX device, the VCO will drift to an unspecified floor frequency. The PLL output clock(s) is then equal to the unspecified VCO floor frequency divided by the output counters for the PLL clock output(s).
Note that the VCO floor frequency can vary from device to device due to process variation.