ps_change2.vhd

可以很好实现一个二进制转换成BCD码的程序

-----------------------------------------------------------------------
--function :parallet in sereis out, high bit first in,first out;
--并串转换，保证n位数全部串行（左移位，高位在前）输出后，再重新自动置数，再转换
--无人为延时
-----------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity ps_change2 is
 generic (n : integer :=14                 --bits of parallet input
          );
 port(in_paral :in std_logic_vector(n-1 downto 0);--parallet input
      clk :in std_logic;
      out_series:out std_logic               --series  output 
      );
end entity;

architecture behave of ps_change2 is
 signal tmp : std_logic_vector(n-1 downto 0);
 signal load: integer range 0 to n;          --load＝0则置数，否则移位输出
begin
process(clk,tmp)
 begin
 if(clk'event and clk='1') then
   if(load=0) then                           --load＝0，置数
     tmp<=in_paral;
     load<=n-1;                                 --置需要移位的次数n
     out_series<=in_paral(n-1);     
   else                                      --load不等于0，移位输出
     out_series<=tmp(n-2);
     tmp(n-1 downto 1)<=tmp(n-2 downto 0);
     load<=load-1;                           --移位一次，load数减一
   end if;
 end if;
end process;      
end behave;