Low Pass IIR filter using cyclone II FPGA

U.Meyer-Baeses digital signal processing with fpga is a profound DSP textbook with a detailed IIR filter chapter. It also has VHDL examples.

I can't see, that the filter is defined recursively in your example (and it probably shouldn't be). But it's strongly recommended to scale the coefficients to a fixed point representation to allow a FPGA suited filter implementation with signed signals. Some filter tools, e. g. Nuhertz Filter Solutions, perform this operation in filter design automaticly. Also MatLab/Octave can do, of course.