xs.vhd

本程序是用VHDL编写

library ieee;                      
use ieee.std_logic_1164.all;
use ieee.std_logic_signed.all;          

entity xs is		 
	port(clk:in std_logic;		
		  --st:in std_logic_vector(1 downto 0);		
		  ho:out std_logic_vector(7 downto 0);		
		  lo:out std_logic_vector(7 downto 0));		
end xs;

architecture xs of xs is
	signal cnt:std_logic_vector(9 downto 0):="0000000000";		
	signal count:std_logic_vector(1 downto 0):="00";		
	signal cou:std_logic_vector(2 downto 0):="000";			
begin
process(clk)
	begin
		if(clk'event and clk='1')then		
			--if st="10" then		
			cnt<=cnt+1;
			--else cnt<="0000000000";
			--end if;
		end if;		
		count(1 downto 0)<=cnt(9 downto 8);		
		cou(2 downto 0)<=cnt(2 downto 0);		
                case cou(2 downto 0) is
					when"000"=>ho<="10000000";
					when"001"=>ho<="01000000";
					when"010"=>ho<="00100000";
					when"011"=>ho<="00010000";
					when"100"=>ho<="00001000";
					when"101"=>ho<="00000100";
					when"110"=>ho<="00000010";
					when"111"=>ho<="00000001";
					when others=>ho<="00000000";
				end case;

			if count="00"then		            --B
				case cou(2 downto 0) is
					when"000"=>lo<="11111111";
					when"001"=>lo<="10000011";
					when"010"=>lo<="10111101";
					when"011"=>lo<="10111101";
					when"100"=>lo<="10000011";
					when"101"=>lo<="10111101";
					when"110"=>lo<="10111101";
					when"111"=>lo<="10000011";
					when others=>lo<="11111111";
				end case;
			elsif count="01"then		       --U
				case cou(2 downto 0) is
					when"000"=>lo<="11111111";
					when"001"=>lo<="10111101";
					when"010"=>lo<="10111101";
					when"011"=>lo<="10111101";
					when"100"=>lo<="10111101";
					when"101"=>lo<="10111101";
					when"110"=>lo<="11000011";
					when"111"=>lo<="11111111";
					when others=>lo<="11111111";
				end case;
			elsif count="10"then		       --P
				case cou(2 downto 0) is
					when"000"=>lo<="11111111";
					when"001"=>lo<="10000011";
					when"010"=>lo<="10111101";
					when"011"=>lo<="10111101";
					when"100"=>lo<="10000011";
					when"101"=>lo<="10111111";
					when"110"=>lo<="10111111";
					when"111"=>lo<="10111111";
					when others=>lo<="11111111";
				end case;
			elsif count="11"then		       --T                                
				case cou(2 downto 0) is
					when"000"=>lo<="11111111";
					when"001"=>lo<="10000011";
					when"010"=>lo<="11101111";
					when"011"=>lo<="11101111";
					when"100"=>lo<="11101111";
					when"101"=>lo<="11101111";
					when"110"=>lo<="11101111";
					when"111"=>lo<="11101111";
					when others=>lo<="11111111";
				end case;
			else ho<="00000000";lo<="11111111";		
			end if;
end process;
end ;