Problem with "WHILE...loop"

The synthesis for the "while" loops is rather complicated as the amount of terms the loop will be taken is not known at compile time. This would mean that separate hardware would be generated for every individual value of the signals to be tested in your while loop.

So the code:

while (n <= 15) loop

would have to be expanded in hardware for every individual case where n = 0, n = 1, n = 2 ... n = 15.

I have the impression that there are a number of states in which you would like to stay for a number of turns (indicated by the end conditions of your while expression).

In the case that your state transitions (also the loops from a state to itself) are taking place synchronized by the clock, you can implement the statemachine by using "if" expressions instead of the "while" loops.

In the "if" expression as long as the end condition is not met, your etat_suivant next state should remain the same as the previous value. Only when the end condition is met, you should update the next state etat_suivant.