vhdl基础---分频

 1 ibrary IEEE;
 2 use IEEE.STD_LOGIC_1164.ALL;
 3 use ieee.std_logic_arith;
 4 use ieee.std_logic_unsigned;
 5 
 6 
 7 entity test_1 is
 8     generic (n: integer:=6);
 9     port(
10             clkin: in std_logic;-----rate=n,n is odd;
11             clkout: out std_logic ---relative FPGA,clkout is out signal;
12     );
13 end test_1;
14 
15 architecture Behavioral of test_1 is
16     signal cnt:integer range 0 to n-1;
17 begin
18     process (clkin)------count
19     begin 
20         if (clkin'event and clkin='1') then 
21             if(cnt<n-1) then
22                 cnt<=cnt+1;
23             else
24                 cnt<=0;
25             end if;
26         end if;
27     end process;
28     
29     process(cnt) -----根据计数值，控制输出始终脉冲的高低电平
30     begin
31         if(cnt<n/2) then
32             clkout<='1';
33         else
34             clkout<='0';
35         end if;
36     end process;
37 
38 
39 end Behavioral;

 1 library IEEE;
 2 use IEEE.STD_LOGIC_1164.ALL;
 3 use ieee.std_logic_arith;
 4 use ieee.std_logic_unsigned;
 5 
 6 
 7 -- Uncomment the following library declaration if using
 8 -- arithmetic functions with Signed or Unsigned values
 9 --use IEEE.NUMERIC_STD.ALL;
10 
11 -- Uncomment the following library declaration if instantiating
12 -- any Xilinx primitives in this code.
13 --library UNISIM;
14 --use UNISIM.VComponents.all;
15 
16 entity test_1 is
17     generic (n: integer:=10);
18     port(
19             clkin: in std_logic;-----rate=n,n is odd;
20             clkout: out std_logic ---relative FPGA,clkout is out signal;
21     );
22 end test_1;
23 
24 architecture Behavioral of test_1 is
25     signal cnt:integer range 0 to n/2-1;
26     signal temp :std_logic;
27 begin
28     process (clkin)------count
29     begin 
30         if (clkin'event and clkin='1') then 
31             if(cnt=n/2-1) then
32                 cnt<=0;
33                 temp<=not temp;
34             else
35                 cnt<=cnt+1;
36             end if;
37         end if;
38     end process;
39     
40     
41     clkout<=temp;---clkout和temp都是信号，均可传出来
42 
43 
44 end Behavioral;

 1 entity test_1 is
 2     generic (n: integer:=5);
 3     port(
 4             clkin: in std_logic;-----rate=n,n is 偶数;
 5             clkout: out std_logic ---relative FPGA,clkout is out signal;
 6     );
 7 end test_1;
 8 
 9 architecture Behavioral of test_1 is
10     signal cnt1,cnt2:integer range 0 to n/2-1;
11     
12 begin
13     process (clkin)------count
14     begin 
15     if (clkin'event and clkin='1') then ------上升沿计数
16         if(cnt1<n-1) then
17                 cnt1<=cnt1+1;
18                 
19             else
20                 cnt1<=0;
21             end if;
22         end if;
23     end process;
24     
25     process (clkin)------count
26     begin 
27     if (clkin'event and clkin='0') then ------下升沿计数
28         if(cnt2<n-1) then
29                 cnt2<=cnt2+1;
30                 
31             else
32                 cnt2<=0;
33             end if;
34         end if;
35     end process;
36     
37     
38     clkout<='1' when cnt1<(n-1)/2 else
39                 '0' when cnt2<(n-1)/2;
40 
41 
42 end Behavioral;

 1 entity test_1 is----占空比3：:1 的偶数分频器
 2                     -----当计数值为0-2时，输出高电平，到计数值为
 3                     ---3-9时，输出低电平
 4     generic (
 5                 n: integer:=10;
 6                 m: integer:=3  ----占空比为m:n,rate=n;
 7                 );
 8     port(
 9             clkin: in std_logic;-----rate=n,n is 偶数;
10             clkout: out std_logic ---relative FPGA,clkout is out signal;
11     );
12 end test_1;
13 
14 architecture Behavioral of test_1 is
15     signal cnt1:integer range 0 to n-1;
16     
17 begin
18     process (clkin)------count
19     begin 
20     if (clkin'event and clkin='1') then ------上升沿计数
21         if(cnt1<n-1) then
22                 cnt1<=cnt1+1;
23                 
24             else
25                 cnt1<=0;
26             end if;
27         end if;
28     end process;
29     
30     
31     
32     clkout<='1' when cnt1<m else
33                 '0' ;
34 
35 
36 end Behavioral;