About VHDL description

Well, without the code, there is not much more that can be done here. You say you can't post it, so without knowing how you are trying to do the conversion that is not working as intended, I don't think you'll be able to get much more help.

Have you simulated the design? Have you used an on-chip debugging tool like Signal Tap? There's lots of other debugging you can perform on your own that maybe you could show us the results of that could help.