entity SlaveN is
  port(
      cs : in std_logic;
      done : out std_logic;
      clk : in std_logic;
      ...);
end SlaveN;

architecture Behavioral of SlaveN is
begin
  process(clk) begin
    if clk'event and clk = '1' then
      if cs = '0' then
        done <= 'Z';
      else completed_pending_job then
        done <= '1';
      else
        done <= '0';
      end if;
    end if;
  end process;
end Behavioral;