VHDL数码管扫描程序调不过……

曾经最美

在我的开发板上这个程序可以让数码管显示22222222：

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity shumaguan is
port(
   clk:in std_logic;
   weiut std_logic_vector(7 downto 0);        
   duanut std_logic_vector(6 downto 0)
);
end entity shumaguan;

architecture shumaguan of shumaguan is
signal wei0:std_logic_vector(7 downto 0) := "01111111";
signal duan0:std_logic_vector(3 downto 0) := "0000";
begin
clk0:process(clk)
begin
   wei <= "00000000"; --位选，低电平有效
end process clk0;
         
clk1:process(clk)
begin
   duan <= "0100100"; --段选，顺序是GFEDCBA，不含小数点
end process clk1;
end architecture shumaguan;

======================================================================

但是把位选和段选换成扫描的方式之后，就什么都不显示了

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity shumaguan is
         port(
                 clk:in std_logic;
                 weiut std_logic_vector(7 downto 0);        
                 duanut std_logic_vector(6 downto 0)
                 );
end entity shumaguan;

architecture shumaguan of shumaguan is
signal wei0:std_logic_vector(7 downto 0) := "01111111";
signal duan0:std_logic_vector(3 downto 0) := "0000";
begin
clk0:process(clk)
begin
   if (wei0="01111111") then
    wei0 <= "10111111";
   elsif (wei0="10111111") then
    wei0 <= "11011111";
   elsif (wei0="11011111") then
    wei0 <= "11101111";
   elsif wei0="11101111" then
    wei0 <= "11110111";
   elsif wei0="11110111" then
    wei0 <= "11111011";
   elsif wei0="11111011" then
    wei0 <= "11111101";
   elsif wei0="11111101" then
    wei0 <= "11111110";
   else
    wei0 <= "01111111";
   end if;
   wei <= wei0;
end process clk0;

clk1:process(clk)
begin
   duan0 <= "0010";
   if duan0="0000" then
    duan <= "1000000";
   elsif duan0="0001" then
    duan <= "1111001";
   elsif duan0="0010" then
    duan <= "0100100";
   elsif duan0="0011" then
    duan <= "0110000";
   elsif duan0="0100" then
    duan <= "0011001";
   elsif duan0="0101" then
    duan <= "0010010";
   elsif duan0="0110" then
    duan <= "0000010";
   elsif duan0="0111" then
    duan <= "1011000";
   elsif duan0="1000" then
    duan <= "0000000";
   elsif duan0="1001" then
    duan <= "0010000";
   else
    duan <= "1000000";
   end if;
end process clk1;
end architecture shumaguan;

不知道写错了哪里，急求帮助啊。。。。。。