The pll_areset port is unconnected in the ALTGX megafunction for Cyclone® IV GX devices in the Quartus® II software version 10.0 and 10.0sp1. The pll_powerdown port is connected to the PLL areset port in this version. Use pll_powerdown for pll_areset functions in version 10.0 and 10.0sp1 of the ALTGX megafunction.
A future release of the Quartus II software will remove the pll_powerdown port in place of the pll_areset port on the ALTGX megafunction. Designs created in version 10.0 and 10.0sp1 will be backward compatible, the pll_powerdown port will still function as PLL areset. New designs created after version 10.0sp1 will need to use pll_areset instead of pll_powerdown.