Altera PLL re-configure

See Altera app note: AN507 - implement PLL reconfiguration in Cyclone III device
http://www.altera.com/literature/an/AN507.pdf

Basically, if only the freqency needs to be changed, the ALTPLL_RECONFIG megafunction can be used and connected with ALTPLL core.

ALTPLL_RECONFIG can have a init file which can be used to re-configure ALTPLL in runtime.

In terms of changing shift phase, it's a bit more work to do, which involves directly control of phase shift interface of ALTPLL_RECONFIG..............