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hi every body i write a vhdl code that is nearly accurate counter every 1.34 s the LED will be ++ (2^27*10ns = 1.34 s ) please tell me what is it's problem because in ISIM i don't got the answer
---------------------------------------------------------------------------------- -- Company: -- Engineer: -- -- Create Date: 08:48:18 09/28/2014 -- Design Name: -- Module Name: count - Behavioral -- Project Name: -- Target Devices: -- Tool versions: -- Description: -- -- Dependencies: -- -- Revision: -- Revision 0.01 - File Created -- Additional Comments: -- ---------------------------------------------------------------------------------- library IEEE; use IEEE.STD_LOGIC_1164.ALL; -- Uncomment the following library declaration if using -- arithmetic functions with Signed or Unsigned values use IEEE.STD_logic_unsigned.ALL; --use IEEE.NUMERIC_STD.ALL; -- Uncomment the following library declaration if instantiating -- any Xilinx primitives in this code. --library UNISIM; --use UNISIM.VComponents.all; entity count is Port ( clk : in STD_LOGIC; reset : in STD_LOGIC; sw1 : in STD_LOGIC; LED : out std_logic_vector(7 downto 0)); end count; architecture Behavioral of count is begin process (clk,reset,sw1) variable c :std_logic_vector(7 downto 0):="00000000"; variable counter :std_logic_vector(27 downto 0):="0000000000000000000000000000"; begin if reset='1' then LED <= "00000000"; elsif sw1='1' then LED <= "11111111"; elsif(clk'event and clk='1') then counter := counter +1 ; if (counter ="1000000000000000000000000000") then c:=c+1; LED<=c; counter:="0000000000000000000000000000"; end if; end if; end process; end Behavioral; |
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just some tipps: - no need to use variables here, use signals instead for the counting logic. (and read about the difference of signals and variables) - it's better style to use IEEE.NUMERIC_STD.ALL to calculate in vhdl and don't calculate with logic_vectors directly, but instead with integer or natural - you can use hex-format for more compact style: x"00" for "00000000"
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First: please use the vhdl tags areund your VHDL code:
[vhdl]VHDL code[/vhdl] |
Then this:
variable counter :std_logic_vector(27 downto 0):="0000000000000000000000000000"; |
Why do you use a variable? Why don't you use an integer? And where did you find this:
if reset='1' then LED <= "00000000"; elsif sw1='1' then LED <= "11111111"; elsif(clk'event and clk='1') then |
An asynchronous reset AND additionally a conbinatorial reset. Thats plain rubbish! This here:
counter:="0000000000000000000000000000";
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Could be shortened to that:
counter:=(others=>'0'); |
Mohammad Mothermohammad wrote: > i write a vhdl code that is nearly accurate My VHDL code usually is exactly accurate. Whats the problem with yours? > please tell me what is it's problem because in ISIM i don't got the answer What error messages do you get? What do you expect and what happens instead? I would do it like this:
library IEEE; use IEEE.STD_LOGIC_1164.ALL; use IEEE.NUMERIC_STD.ALL; entity BlinkLED is Port ( clk : in STD_LOGIC; led : out STD_LOGIC); end BlinkLED; architecture Behavioral of BlinkLED is -- let the synthesizer do the hard work! signal c : integer range 0 to 1340000000/10-1 := 0; -- 1.34s at 100MHz = 1340000000ns/10ns signal x : std_logic:= '0'; begin process begin wait until rising_edge(clk); -- wait till next clock if (c<1340000000/10-1) then -- check the counter c <= c+1; -- if less: count up else -- if reached: c <= 0; -- reset counter x <= not x; -- and toggle the local signal x end if; end process; led <= x; -- hand x over to the LED end Behavioral; |
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thank you for every one i modified the code and implement this into FPGA and it's work. correct code is:
---------------------------------------------------------------------------------- -- Company: -- Engineer: -- -- Create Date: 08:48:18 09/28/2014 -- Design Name: -- Module Name: count - Behavioral -- Project Name: -- Target Devices: -- Tool versions: -- Description: -- -- Dependencies: -- -- Revision: -- Revision 0.01 - File Created -- Additional Comments: -- ---------------------------------------------------------------------------------- library IEEE; use IEEE.STD_LOGIC_1164.ALL; -- Uncomment the following library declaration if using -- arithmetic functions with Signed or Unsigned values use IEEE.STD_logic_unsigned.ALL; --use IEEE.NUMERIC_STD.ALL; -- Uncomment the following library declaration if instantiating -- any Xilinx primitives in this code. --library UNISIM; --use UNISIM.VComponents.all; entity count is Port ( clk : in STD_LOGIC; reset : in STD_LOGIC; sw1 : in STD_LOGIC; LED : out std_logic_vector(7 downto 0)); end count; architecture Behavioral of count is begin process (clk,reset,sw1) variable c :std_logic_vector(7 downto 0):="00000000"; variable counter :std_logic_vector(26 downto 0):="000000000000000000000000000"; begin if(clk'event and clk='1') then if reset='1' then LED <= "00000000"; counter := "000000000000000000000000000"; c:="00000000"; elsif sw1='1' then LED <= "11111111"; c := "11111111"; LED <=c; -- for i in 0 to 10000000 loop -- if (i=10000000) then -- counter:="000000000000000000000000000"; -- c:="00000000"; -- LED <= c; --end if; -- end loop ; else counter := counter +1 ; if (counter ="101111101011110000100000000") then c:=c+1; LED<=c; counter:="000000000000000000000000000"; end if; end if; end if; end process; end Behavioral; |
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