交通灯的数码管显示

LIBRARY ieee;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.STD_LOGIC_ARITH.ALL;

use IEEE.STD_LOGIC_UNSIGNED.ALL;

ENTITY display IS

PORT(

clk_1k : IN STD_LOGIC;--时钟输入

ch,cl : IN std_logic_vector(3 downto 0);

chip_sel : OUT STD_LOGIC_VECTOR(2 downto 0);

segout : OUT STD_LOGIC_VECTOR(6 downto 0)

);

END display;

ARCHITECTURE one OF display IS

begin

process(clk_1k)

variable kk : std_logic;--位选信号

FUNCTION b_to_s7(bcd8421:std_logic_vector(3 downto 0)) RETURN STD_LOGIC_VECTOR IS

V ARIABLE smg7: STD_LOGIC_VECTOR(6 DOWNTO 0);

BEGIN

CASE bcd8421 IS --计算输出值

WHEN "0000" => smg7:="1111110"; --abcdefg

WHEN "0001" => smg7:="0110000"; --共阴数码管

WHEN "0010" => smg7:="1101101";

WHEN "0011" => smg7:="1111001";

WHEN "0100" => smg7:="0110011";

WHEN "0101" => smg7:="1011011";

WHEN "0110" => smg7:="1011111";

WHEN "0111" => smg7:="1110000";

WHEN "1000" => smg7:="1111111";

WHEN "1001" => smg7:="1111011";

WHEN OTHERS=>

END CASE;

RETURN smg7;

END b_to_s7;

begin

if rising_edge(clk_1k) then

kk:= not kk;

chip_sel<=(0=>kk,others=>'0');--选用后两个数码管

end if;

if kk='1' then

segout<=b_to_s7(ch);

else segout<=b_to_s7(cl);

end if;

end process;

end one;