http://vhdlguru.blogspot.com/2010/03/digital-clock-in-vhdl.html
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
entity digi_clk is
port (clk1 : in std_logic;
seconds : out std_logic_vector(5 downto 0);
minutes : out std_logic_vector(5 downto 0);
hours : out std_logic_vector(4 downto 0)
);
end digi_clk;
architecture Behavioral of digi_clk is
signal sec,min,hour : integer range 0 to 60 :=0;
signal count : integer :=1;
signal clk : std_logic :='0';
begin
seconds <= conv_std_logic_vector(sec,6);
minutes <= conv_std_logic_vector(min,6);
hours <= conv_std_logic_vector(hour,5);
--clk generation.For 100 MHz clock this generates 1 Hz clock.
process(clk1)
begin
if(clk1'event and clk1='1') then
count <=count+1;
if(count = 50000000) then
clk <= not clk;
count <=1;
end if;
end if;
end process;
process(clk) --period of clk is 1 second.
begin
if(clk'event and clk='1') then
sec <= sec+ 1;
if(sec = 59) then
sec<=0;
min <= min + 1;
if(min = 59) then
hour <= hour + 1;
min <= 0;
if(hour = 23) then
hour <= 0;
end if;
end if;
end if;
end if;
end process;
end Behavioral;
