arbitro

arbito.vhd

LIBRARY ieee;
USE ieee.std_logic_1164.all;

ENTITY arbitro IS
  PORT
  (
      Clock, Reset: IN STD_LOGIC;
      r: IN STD_LOGIC_VECTOR (1 TO 3);
      c: OUT STD_LOGIC_VECTOR (1 TO 3)
  );
END arbitro;

ARCHITECTURE comportamento OF arbitro IS
  TYPE Tipo_estado IS (BD, D1, D2, D3);
  SIGNAL y: Tipo_estado;
  BEGIN
    PROCESS (Reset, Clock)
      BEGIN
        IF Reset = '1' THEN y <= BD;
        ELSIF (Clock'EVENT AND Clock = '1') THEN
          CASE y IS
            WHEN BD =>
              IF r(1)= '1' THEN y <= D1;
              ELSIF r(2)= '1' THEN y <= D2;
              ELSIF r(3)= '1' THEN y <= D3;
              ELSE y <= BD;
              END IF ;
            WHEN D1 =>
              IF r(1)= '1' THEN y <= D1;
              ELSE r(1) = '0';
              END IF;
            WHEN D2 =>
              IF r(2)= '1' AND r(1)= '0' THEN y <= D2;
              ELSE r(2) = '0';
              END IF;
            WHEN D3 =>
              IF r(3)= '1' AND r(2)= '0' AND r(1)= '0' THEN y <= D3;
              ELSE r(1) = '0';
              END IF;
         END CASE;
      END IF;
   END PROCESS;
   WITH y SELECT
     c <= "000" WHEN BD,
          "001" WHEN D1,
          "010" WHEN D2,
          "100" WHEN D3;
END comportamento;

arbitro2.vhd

LIBRARY ieee;
USE ieee.std_logic_1164.all;

ENTITY arbitro IS
  PORT
  (
      Clock, Reset: IN STD_LOGIC;
      r: IN STD_LOGIC_VECTOR (1 TO 3);
      c: OUT STD_LOGIC_VECTOR (1 TO 3)
  );
END arbitro;

ARCHITECTURE comportamento OF arbitro IS
  TYPE Tipo_estado IS (BD, D1, D2, D3);
  SIGNAL y: Tipo_estado;
  BEGIN
    PROCESS (Reset, Clock)
      BEGIN
        IF Reset = '1' THEN y <= BD;
        ELSIF (Clock'EVENT AND Clock = '1') THEN
          CASE y IS
            WHEN BD =>
              IF r(1)= '1' THEN y <= D1;
              ELSIF r(2)= '1' THEN y <= D2;
              ELSIF r(3)= '1' THEN y <= D3;
              ELSE y <= BD;
              END IF ;
            WHEN D1 =>
              IF r(1)= '1' THEN y <= D1;
              ELSE y <= BD;
              END IF;
            WHEN D2 =>
              IF r(1)= '0' AND r(2)= '1' THEN y <= D2;
              ELSE y <= BD;
              END IF;
            WHEN D3 =>
              IF r(1)= '0' AND r(2)= '0' AND r(3)= '1' THEN y <= D3;
              ELSE y <= BD;
              END IF;
         END CASE;
      END IF;
   END PROCESS;
   WITH y SELECT
     c <= "000" WHEN BD,
          "001" WHEN D1,
          "010" WHEN D2,
          "100" WHEN D3;
END comportamento;