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-- Company:            ISI/Nallatech

-- Engineer:           Luis Munoz

-- Email:              lfmunoz4@gmail.com

-- 

-- Create Date:        06:01:23 01/01/2011 

--

-- Module Name:        XCOUNTER - Behavioral 

--

-- Project Name:       Counter

--

-- Target Devices:     Any

--

-- Description:        This module increments on the risinge edge of CLK_i when CLKen_i 

--                     is high. It counts from 0 to XVAL and wraps around, on the last value,

--                     XVAL, DONE_o goes high.

--

-- Revision:           1.0 Initial Release

--

-- Additional Comments: 

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library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity xcounter is

generic(

    XVAL      : std_logic_vector := x"3"

);

port(

    CLK_i     : in std_logic;

    RST_i     : in std_logic;

    CLKen_i   : in std_logic;

    COUNT_o   : out std_logic_vector(XVAL'length-1 downto 0);

    DONE_o    : out std_logic

);

end xcounter;

architecture Behavioral of xcounter is

   constant lastVal        : std_logic_vector(XVAL'length-1 downto 0) := XVAL;

   signal   counter_r      : std_logic_vector(XVAL'length-1 downto 0);

begin

-------------------------------------------------

    process(CLK_i, CLKen_i, RST_i)

    begin

        if rising_edge(CLK_i) then

            if(RST_i = '1') then

                counter           <= (others=>'0');

            elsif( CLKen_i = '1') then

                if( counter_r = lastVal) then

                    counter_r     <= (others=>'0');

                else

                    counter_r     <= counter_r + 1;

                end if;

            end if;

        end if;

    end process;

    -- two output signals done and the counter value

    DONE_o    <= '1' when counter_r = lastVal  else '0';

    COUNT_o   <= counter_r;

-------------------------------------------------

end Behavioral;