multiple constant drivers error

Thanks for help !

The code of the post# 5 work but stop at the first When ...

So I go to try with the two first process but with the Frank's architecture.

NB: etat_pres = curent statement

etat_suiv = next statement

So what's right?

etat_pres <= etat_suiv;

or

etat_suiv<= etat_pres ;

When I had this process

Process(clock)
begin
  if rising_edge(clock) then 
  etat_suiv <= etat_pres;
end if;
end process;

I get the same error ( multiple constant drivers)

and when I had this

Process(clock)
begin
  if rising_edge(clock) then 
  etat_pres <= etat_suiv;
end if;
end process;

no error but the code dont take effect.