-- The Electronic Gardener
--
-- Mark Kudryk, Kim Ellis
--
-- Module Name: devtimer.vhd
-- Author: Kim Ellis
-- Date: November 07, 1998
-- Status: Completed
---------------------------------------------------------------
-- Description:
--   Device Timer Module for Spot Watering
--   The timer counts down from a fixed setting,
--   producing a timeout signal for the device state machine
---------------------------------------------------------------

library ieee;
use ieee.std_logic_1164.all;
use IEEE.std_logic_arith.all;
use IEEE.std_logic_unsigned.all;

entity devtimer is
    port( reset          : in  std_logic;
          second         : in  std_logic;

          timer_moist    : in  std_logic;
          timeout_moist  : buffer std_logic     );
end devtimer;

architecture a of devtimer is
    constant sec_30 : std_logic_vector(5 downto 0) :="011110";
    signal count_moist : std_logic_vector( 5 downto 0 );
begin

    process( second, reset )
    begin

        if reset = '1' then
            timeout_moist <= '1';
            count_moist <= sec_30;

         elsif rising_edge( second ) then

            if (timer_moist = '0' and timeout_moist = '0') then

                if count_moist /= "000000" then
                    count_moist <= count_moist - '1';
                    timeout_moist <= '0';
                else
                    timeout_moist <= '1';
                    count_moist <= sec_30;
                end if;

            elsif (timer_moist = '1' and timeout_moist = '1') then
                timeout_moist <= '0';

            elsif timer_moist = '1' and timeout_moist='0' then
                count_moist <= sec_30;

            end if;

        end if;

    end process;

end a;