PACKAGE waiting IS
  TYPE wait_array IS ARRAY (NATURAL RANGE <>) OF NATURAL;
END waiting;
--
USE WORK.waiting.ALL;  
ENTITY arbitrator IS
  GENERIC (wait_states : wait_array := (0, 1, 2, 3); 
           clock_period : TIME := 1 US);
  PORT (request : IN BIT_VECTOR (3 DOWNTO 0); 
        grant : BUFFER BIT_VECTOR (3 DOWNTO 0); clock : IN BIT);
END arbitrator;
--
ARCHITECTURE behavioral OF arbitrator IS
BEGIN
  wait_cycle: PROCESS 
  BEGIN
    IF clock = '0' THEN
      WAIT FOR 20 NS;
      FOR i IN request'RANGE LOOP
        IF request(i) = '1' THEN
          IF grant = "0000" THEN 
            WAIT FOR wait_states (i) * clock_period;
            grant (i) <= '1', '0' AFTER clock_period;
          END IF;
        END IF; 
      END LOOP;
    END IF;
    WAIT ON clock;
  END PROCESS wait_cycle;
END behavioral;
--

ENTITY arbtest IS END arbtest;
--
ARCHITECTURE io OF arbtest IS
  USE WORK.waiting.ALL;
  CONSTANT source_delays : wait_array := (12, 10, 9, 14);
  SIGNAL clk : BIT;
  SIGNAL r, g : BIT_VECTOR (3 DOWNTO 0);
  CONSTANT t : TIME := 1 US;
BEGIN
  arb : ENTITY WORK.arbitrator (behavioral)
    GENERIC MAP (wait_states => (3 => 0, 2 => 1, 1 => 2, 0 => 3), clock_period =
> t)
    PORT MAP (r, g, clk);
  clk <= NOT clk AFTER t / 2 WHEN NOW < 40 US ELSE clk;
  sources : FOR i IN  r'RANGE GENERATE
    PROCESS
    BEGIN
      WAIT FOR source_delays (i) * 1 US;
      r(i) <= '1';
      WAIT UNTIL g(i) = '1';
      WAIT UNTIL clk = '0';
      r(i) <= '0';
    END PROCESS;
  END GENERATE;
--r <= (r1, r2, r3, r4);
--(g1, g2, g3, g4) <= g;
END io;