Also, comparing the output to zero seems easy, but how to i check if it is less than zero?
Sorry I missed the second half of the question. I'm at work and somebody interrupted me in the middle of typing...
Don't think of testing for less than 0; rather test for negative. What bit of a binary number indicates that it is a negative number?
If you haven't found it yet, one thing that can simplify you status output code is that just like you can solder more than one wire to a physical part's output, you can have more than one "out=" on an HDL part.
Check out the example in appendix A
, section A.5.3