Modelsim - VHDL common question.

Some warnings are related to code not shown in your post. Y1, Y2 are inputs in the shown code, not registers.

Some warnings are directly brought up by your code, you should be able to see the cause when looking sharp.

Warning (13410): Pin "Yn" stuck at GND
Warning (13410): Pin "Yn" stuck at GND

Not surprizing considering the assignment

Yn <=   (addr(15) & addr(12 downto 0) & "00");

Because the post is only showing part of the filter code, I can't determine if it's operating according to your intentions now. You also didn't report the results for the final version. The warnings can be considered "normal operation" so far.

As a general remark, I guess that the filter will be affected by arithmetic overflows with respective input data. Or did you downscale the coefficients to prevent it for all possible input values? But then, you would loose a lot of available dynamic.

I also doubt, that you'll save much resources by time-multiplexing an adder and a multiplier compared to a full pipelined design using multiple adders and multipliers.