Simple implementation of finite-state machine

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-- Company:
-- Engineer:
--
-- Create Date:    23:36:39 12/12/2014
-- Design Name:
-- Module Name:    MainModule - Behavioral
-- Project Name:
-- Target Devices:
-- Tool versions:
-- Description:
--
-- Dependencies:
--
-- Revision:
-- Revision 0.01 - File Created
-- Additional Comments:
--
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library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
--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 MainModule is
    Port ( iCLK : in  STD_LOGIC;
           inRST : in  STD_LOGIC;
           iSEL : in  STD_LOGIC_VECTOR (1 downto 0);
           iDURATION : in  STD_LOGIC_VECTOR (7 downto 0);
           iSTART : in  STD_LOGIC;
           o150W : out  STD_LOGIC;
           o300W : out  STD_LOGIC;
           o650W : out  STD_LOGIC;
           o800W : out  STD_LOGIC;
           oWARN : out  STD_LOGIC);
end MainModule;

architecture Behavioral of MainModule is

-- FSM
type tSTATES is (IDLE, HEAT, WARNING);
signal sSTATE: tSTATES;
signal sWarn_EN: STD_LOGIC;
signal sHeat_EN: STD_LOGIC;

-- WarnCounter
signal sWarnCNT: STD_LOGIC_VECTOR(2 downto 0);
signal sWarnCNT_TC: STD_LOGIC;
signal sWarnCNT_EN: STD_LOGIC;

-- HeatCounter
signal sHeatCNT: STD_LOGIC_VECTOR(7 downto 0);
signal sHeatCNT_TC: STD_LOGIC;
signal sHeatCNT_EN: STD_LOGIC;

begin
    WarnCounter: process (iCLK, inRST) begin
        if (inRST = '0') then
            sWarnCNT <= (others => '0');
            sWarnCNT_TC <= '0';
        elsif (rising_edge(iCLK)) then
            if (sWarnCNT_EN = '1') then
                if (sWarnCNT = 7) then
                    sWarnCNT_TC <= not sWarnCNT_TC;
                    sWarnCNT <= (others => '0');
                else
                    sWarnCNT <= sWarnCNT + 1;
                end if;
            end if;
        end if;
    end process;

    HeatCounter: process (iCLK, inRST) begin
        if (inRST = '0') then
            sHeatCNT <= (others => '0');
            sHeatCNT_TC <= '0';
        elsif (rising_edge(iCLK)) then
            if (sHeatCNT_EN = '1') then
                if (sHeatCNT = iDURATION - 1) then
                    sHeatCNT_TC <= not sHeatCNT_TC;
                    sHeatCNT <= (others => '0');
                else
                    sHeatCNT <= sHeatCNT + 1;
                end if;
            end if;
        end if;
    end process;

    FSM: process (iCLK, inRST) begin
        if (inRST = '0') then
            sSTATE <= IDLE;
            sHeatCNT_EN <= '1';
            sWarnCNT_EN <= '1';
        elsif (rising_edge(iCLK)) then
            case (sSTATE) is
                when IDLE => sHeatCNT_EN <= '0';
                            sWarnCNT_EN <= '0';
                            sWarn_EN <= '0';
                            sHeat_EN <= '0';

                            if (iSTART = '1') then
                                sSTATE <= HEAT;
                            end if;

                when HEAT => sHeatCNT_EN <= '1';
                            sWarnCNT_EN <= '0';
                            sWarn_EN <= '1';
                            sHeat_EN <= '0';

                            if (sHeatCNT_TC = '1') then
                                sSTATE <= WARNING;
                            end if;

                when WARNING => sHeatCNT_EN <= '0';
                            sWarnCNT_EN <= '1';
                            sWarn_EN <= '0';
                            sHeat_EN <= '1';

                            if (sWarnCNT_TC = '1') then
                                sSTATE <= IDLE;
                            end if;
            end case;
        end if;
    end process;

    oWARN <= sWARN_EN;

    -- Demux
    o150W <= sHEAT_EN when iSEL = "00" else '0';
    o300W <= sHEAT_EN when iSEL = "01" else '0';
    o650W <= sHEAT_EN when iSEL = "10" else '0';
    o800W <= sHEAT_EN when iSEL = "11" else '0';

end Behavioral;