www.pudn.com > DDSforsinandcos.rar > cnt8bit.vhd

library ieee; 
use ieee.std_logic_1164.all; 
use ieee.std_logic_unsigned.all; 
 entity cnt8bit is 
  port( 
   en : in std_logic; 
   nreset : in std_logic; 
   clk :in std_logic; 
   co  :out std_logic; 
   qout : buffer std_logic_vector(7 downto 0)); 
end cnt8bit; 
 architecture behave of cnt8bit is 
  begin 
     co<='1'when(qout="11111111") else '0'; 
    process(clk,nreset,en) 
  begin  
     if(nreset='1')then 
     qout<="00000000"; 
      elsif(nreset='0'and en='1')then 
          qout<=qout; 
    elsif(clk'event and clk='1')then 
    qout<=qout+1; 
 end if; 
 
end process; 
 end behave;