priority.vhd

128-64点阵液晶模块的显示程序带反显平移等功能.rar,非常实用.

-- coder is described in this projiect
-- D0~D7 are input vectors
-- Q0~Q2 are the output of the cording
--------------------------------------------------------------------
LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
entity priority is
        port(D : in bit_vector(0 to 7);   --inputs to be prioritised
	    E1 : in bit;
             Q : out bit_vector(0 to 2);  --encoded output
	    E0 : out bit;
            GS : out bit);                --group signal output
end priority;
-------------------------------------------------------------------
architecture coder of priority is
begin
        process(D,E0)
        begin
		if E1 = '1'then				
                	GS <= '1'; --set default outputs
			E0 <= '1';
                	Q <= "111";
		elsif D(7) = '0' then
                        Q<= "000";
						GS <= '0';
						E0 <= '1';
                elsif D(6) = '0' then
                       Q <= "001";
						GS <= '0';
						E0 <= '1';
                elsif D(5) = '0' then
                        Q <= "010";
						GS <= '0';
						E0 <= '1';
                elsif D(4) = '0' then
                        Q <= "011";
						GS <='0';
						E0 <= '1';
                elsif D(3) = '0' then
                        Q <= "100";
						GS <='0';
						E0 <= '1';
                elsif D(2) = '0' then
                        Q <= "101";
						GS <='0';
						E0 <= '1';
                elsif D(1) = '0' then
                        Q <= "110";
						GS <='0';
						E0 <= '1';
                elsif I(0) = '0' then
                        Q <= "111";
						GS <='0';
						E0 <= '1';
                else						
                        Q <="111";
                                                GS <= '1';   
						E0 <= '0';
                end if;
        end process;    
end coder;