syn_gen.vhd

很多仪器都输出同步时钟

library ieee;
use ieee.std_logic_1164.all;
use ieee. std_logic_unsigned.all;
entity syn_gen is
port(clk,syn_in:in std_logic;
     syn_out:out std_logic
    ); 
end syn_gen;

architecture rtl of syn_gen is 
signal syn_flag:std_logic;
signal syn_count:std_logic_vector(14 downto 0);
begin
process(syn_in)
begin
if(syn_count=25000) then
   syn_flag<='0';
elsif(syn_in'event and syn_in='0') then
   syn_flag<='1';
end if;
end process;

syn_out<=syn_flag;

process(clk)
begin
if(clk'event and clk='1') then 
   if(syn_flag='1') then
      syn_count<=syn_count+'1';
   else
      syn_count<=(others=>'0');
   end if;
end if;
end process; 


end rtl;