shift.vhd

2FSK调制功能

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
entity shift is
 port(
   clk:in std_logic;
   do:out std_logic_vector(1 downto 0)
   );
end shift;
architecture a of shift is
signal clkout1:std_logic_vector(9 downto 0);
signal a:std_logic_vector(1 downto 0);
begin
process(clk)

begin
if (clk'event and clk='1') then
   if clkout1="1111111111" then
       clkout1<="0000000000";
       a<= a+1;       
   else
       clkout1<=clkout1+1;
   end if;
end if;
end process;
do<=  a;
end a;