normal I/O to PLL input

HI,

in my design i want to use normal i/o as PLL input in STARTIX2 device. in place and route time it showing error like "PLL input must be A CLKIN pin". is there a any alternative way to resolve this problem.

design change is not possible.

i studied "clocked control block" can use for driving the PLL. but its not working.

please tell me how to resolve this problem.

Thanks & regards

--Ramanand