Electronic – a safe state machine

I finally found that problem was that I have been loading the same design over and over.. So I thought that I have design that light the led but there was none.. Now it works as expected. because I thought that *.MCS files are generated only once not that I have to generate MCS file from BIT file every time I change bitstream.. now it is working, my problem now is that some of packets doesn't go intact through FT245.. I'll make simple acknowledge protocol to fix that.

So this code generates a 200 Hz clock based on a 100 Mhz clock.

We note that: 100 MHz / 500000 = 200 Hz

So, we need to take our 100 Mhz clock, and every 500000 cycles, we would have a full cycle of the 200 Hz clock that we would like to generate. Since we want the high time and low time to be the same, we know that we should oscillate the new clock every 500000 / 2 cycles.

From the perspective of the code, we will use hexadecimal, so it's worth noting that 500000 / 2 == 0x3D090.

architecture foo of blah is
    signal clk_200Hz : std_logic := '0';
    signal counter : unsigned(19 downto 0) := x"00000";
begin

    clkdiv : process (clk_100Mhz)
    begin
        if rising_edge(clk_100Mhz) then
            if counter = x"00000" then
                counter <= X"3D090"
                clk_200Hz <= not clk_200Hz;
            else
                counter <= counter - 1;
            end if;
        end if;
    end process clkdiv;

end architecture;