原创 VHDL 例程---优先级编码器

13:33:48 UTC+0800Wed Jan 9 2008

-- Highest Priority Encoder

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
entity priority is
        port(I : in bit_vector(7 downto 0); --inputs to be prioritised
                A : out bit_vector(2 downto 0); --encoded output
                GS : out bit);  --group signal output
end priority;

architecture v1 of priority is
begin
        process(I)
        begin
                GS <= '1'; --set default outputs
                A <= "000";
                if I(7) = '1' then
                        A <= "111";
                elsif I(6) = '1' then
                        A <= "110";
                elsif I(5) = '1' then
                        A <= "101";
                elsif I(4) = '1' then
                        A <= "100";
                elsif I(3) = '1' then
                        A <= "011";
                elsif I(2) = '1' then
                        A <= "010";
                elsif I(1) = '1' then
                        A <= "001";
                elsif I(0) = '1' then
                        A <= "000";
                else
                        GS <= '0';
                end if;
        end process;    
end v1;